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CommunicationTeam.org Lab Guide for Java Programming

Version No. 1.0 1 of 68

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Lab Guide for Java Programming

CommunicationTeam.org



Contents

THICOPYRIGHT NOTICE .................................................................................................. 1

COPYRIGHT NOTICE ............................................................. ERROR! BOOKMARK NOT DEFINED.

DOCUMENT REVISION HISTORY ............................................... ERROR! BOOKMARK NOT DEFINED.

CONTENTS .................................................................................................................. 2

1 CONTEXT ................................................................................................................. 4

2 ASSIGNMENTS FOR DAY 1 JAVA PROGRAMMING ............................................................. 4

ASSIGNMENT 1: OOAD OF TELE-COMMUNICATION COMPANY ............................................................... 4

ASSIGNMENT 2: USAGE OF ARRAY .......................................................................................... 5

ASSIGNMENT 3: MULTI-DIMENSIONAL ARRAYS ............................................................................... 7

ASSIGNMENT 4: CREATING A CLASS AND OBJECT ........................................................................... 9

ASSIGNMENT 5: PROBLEM DESCRIPTION TO JAVA PROGRAM .............................................................. 11

ASSIGNMENT 6: INITIALIZING THE CLASS MEMBER VARIABLES .............................................................. 11

ASSIGNMENT 7: ARCHITECTURAL NEUTRALITY OF JVM ................................................................... 12

ASSIGNMENT 8: UNDERSTANDING CLASSES ................................................................................ 13

ASSIGNMENT 9: METHOD OVERLOADING .................................................................................. 15

ASSIGNMENT 10: UNDERSTANDING CONSTRUCTORS ...................................................................... 18

ASSIGNMENT 10.A: UNDERSTANDING CONSTRUCTORS .................................................................... 18

ASSIGNMENT 10.B: UNDERSTANDING CONSTRUCTORS .................................................................... 20

ASSIGNMENT 10.C: UNDERSTANDING CONSTRUCTORS .................................................................... 22

ASSIGNMENT 10.D: UNDERSTANDING CONSTRUCTORS .................................................................... 23

ASSIGNMENT 11: ARRAYS OF OBJECTS ................................................................................... 25

3 ASSIGNMENTS FOR DAY 2 JAVA PROGRAMMING ........................................................... 27

ASSIGNMENT 12: STATIC CONCEPTS ...................................................................................... 27

ASSIGNMENT 12.A: STATIC CONCEPTS – STATIC VARIABLES ............................................................... 28

ASSIGNMENT 12.B: STATIC CONCEPTS - STATIC BLOCKS ................................................................. 29

ASSIGNMENT 12.C: STATIC CONCEPTS – PRIVATE CONSTRUCTORS AND STATIC METHODS .................................. 29

ASSIGNMENT 13: INHERITANCE ........................................................................................... 31

ASSIGNMENT 14: UNDERSTANDING INHERITANCE ......................................................................... 32

ASSIGNMENT 15: UNDERSTANDING DYNAMIC BINDING .................................................................... 36

ASSIGNMENT 16: UNDERSTANDING ABSTRACT CLASS ...................................................................... 38

ASSIGNMENT 17: UNDERSTANDING DYNAMIC BINDING .................................................................... 41

ASSIGNMENT 18: UNDERSTANDING INTERFACE ............................................................................ 43

ASSIGNMENT 19: UNDERSTANDING PACKAGES ............................................................................ 44

ASSIGNMENT 20: UNDERSTANDING THE ACCESS SPECIFIER ................................................................ 45

ASSIGNMENT 21: GARBAGE COLLECTION ................................................................................. 48

ASSIGNMENT 21A: GARBAGE COLLECTION ................................................................................ 49

ASSIGNMENT 21B: GARBAGE COLLECTION ................................................................................ 50




ASSIGNMENT 22: AUTOBOXING AND UNBOXING ........................................................................... 51

ASSIGNMENT 23: UNDERSTANDING EXCEPTION HANDLING (UNCHECKED EXCEPTIONS) .................................... 52

ASSIGNMENT 24: UNDERSTANDING EXCEPTION HANDLING – TRY, CATCH & FINALLY ...................................... 55

ASSIGNMENT 25: UNDERSTANDING EXCEPTION HANDLING (CHECKED EXCEPTIONS) ....................................... 56

ASSIGNMENT 26: UNDERSTANDING USER DEFINED EXCEPTION HANDLING ................................................. 57


ASSIGNMENT 27: JAVABEANS ............................................................................................. 59

ASSIGNMENT 28: CREATING (JAVA BEAN) CLASSES AND OBJECT ......................................................... 60

ASSIGNMENT 29: USAGE OF „THIS‟ KEYWORD ............................................................................. 63

ASSIGNMENT 30: UNDERSTANDING COLLECTION FRAMEWORK ............................................................ 65

ASSIGNMENT 31: REFLECTION API ....................................................................................... 65

ASSIGNMENT 32: ANNOTATIONS .......................................................................................... 67



1 Context

This document contains assignments to be completed as part of the hands on for the subject

Java programming

In order to complete the course, assignments in this document must be completed in

the sequence mentioned.

Create a workspace on your desktop with the name “Java” for the assignments.

Under the “Java” folder,create project with names depending upon the day of

assignment. If it is day 1 , create a project with the name “day1” in the “Java”

workspace. Now for every assignment create a separate package. If some assignment

requires multiple packages ( as in case of package assignments ) then create the

nested packages. For example , assume your assignment is “assignment1” and you

need to create two packages in this assignment ( “pack1” and “pack2” ) then you will

be creating two packages with names “pack1” and “pack2” under package

“assignment1”.

2 Assignments for Day 1 Java Programming

Assignment 1: OOAD of Tele-Communication Company

A telecom company wants to automate their process of giving mobile and internet

connections and bill generation. The company has a set of customers. Each customer has a

unique Customer ID, name and address.

Telecom company offers two types of plans for their customers:

a) Mobile Plans

b) Internet Plans

Mobile Plans can be of two types: Pre-paid or Post-paid.

Internet Plans can also be of two types: Business Plan and Home Plan.

A customer can have multiple plans. When the customer opts for a plan, he will be given a

unique user-id and password for the specific plan. Bill should be generated at the end of

every month for every customer.

Identify the classes for the above problem.

Solution:



Assignment 2: Usage of array

Objective: To understand the usage of array.

Problem Description: To calculate the feedback of 5 employees and grade them according to their feedback. Estimated time: 20 Mins.

Step 1: Create a package for the assignment.

Step 2: Open a Eclipse ganymede IDE and create a java file with the name EmployeeGrade

:

Filename EmployeeGrade.java



/*

* This java file is a program to calculate the average feedback

* of 5 employees and determine their grade

*/

/**

* This class will display the grade of 5 employees according

* to their feedback.

* Date : <<Replace with the date you do this assignment>>

* @author <<Replace with your Emp No. & Name>>

* @version 1.0

*/

public class EmployeeGrade {

/**

* Calculates the average feedback of 5 employees and determines

* their grade

* @param args: Command line arguments

*/

public static void main (String [] args) {

//To-do: Calculate the average feedback of all the

employees

//To-do: Determine the grade of all the employees

}

}

Save the file as „EmployeeGrade.java‟.

Follow the below mentioned steps to complete the program

Step 3: Inside the main method, declare 4 arrays for storing the employee numbers,

customer1Feedback, customer2Feedback and customer3Feedback of 5 employees. Initialize

them to any value.

For e.g.

int employeeId[]={1001,1002,1003,1004,1005};

float customer1Feedback[]={4.1f, 3.8f, 4.5f, 4.9f, 3.9f};

Assume employeeId[0] i.e. 1001 has customer 1 feedback as

customer1Feedback[0] i.e. 4.1 and so on

Step 4: Declare a float array averageFeedback [] to store the average feedback of all the

employees.

Step 5: Declare a char array grade [] to store the grade of all the employees.



Step 6: Calculate the average feedback and determine the grade . Store the average

feedback of all the employees in averageFeedback [] array and the grades in grade[] array.

Use looping control statements to access the values from the arrays.

Step 7: Display the employee number, average feedback and grade of all the employees.

Step 8: Compile EmployeeGrade.java. Resolve the errors if any, and recompile the program.

Step 9: Execute EmployeeGrade.java.

Summary of this exercise:

You have just learnt

To declare, initialize and access arrays.

To use looping control statements.

Assignment 3: Multi-dimensional Arrays

Objective: To understand the two-dimensional arrays. Problem Description: Create a class EmployeeFeedback that stores the employee number and the feedback from their customers. Note: Not necessarily, all the employees would have the same number of customers. Estimated time: 15 Mins.

Step 1: Create a package for the assignment.

Step 2: Open Eclipse ganymede IDE and type the following:

Filename EmployeeFeedback.java

/*

* This java file is a program to store and display the employee

* number and their feedback from the customer.

*/

/**

* This class will display the feedback of all the employees





* @version 1.0

*/

public class EmployeeFeedback {

/**

* Stores and displays the feedback of the employees from their

* customer


*/


int [][]empInfo = {{1001,4,5}, {1002,2,4,5}};

for (int outerLoop=0;outerLoop<2;outerLoop++) {

for (int innerLoop=0;innerLoop<3;innerLoop++) {

System.out.println(empInfo[outerLoop][innerLoop]);

}

}

}

}

Save the file as „EmployeeFeedback.java‟

Step 3: Compile and execute the code.

Now, 1001 has feedback from 2 customers and 1002 has feedback from 3

customers. Do you get to display all the values? You would get run-time

exception, if you try to change the upper limit of the array from 3 to 4.

(Analyze and find out the reason). Now, instead of mentioning the constant

as upper limit for the array, use the length property.

for (int outerLoop=0;outerLoop<empInfo.length;outerLoop++)

{

for (int innerLoop=0;innerLoop<empInfo[outerLoop].length;

innerLoop++)

{

System.out.println(empInfo[outerLoop][innerLoop]);

}

}

Step 4: Do the modification in the program, compile and execute the code.


You have learnt

Usage of length property of array



In java, the best practice is always to use the length property instead of the constant

as value for upper limit of the array.

Assignment 4: Creating a Class and Object

Objective: To understand how to create a class and instantiate it. Problem Description: Create a class Customer with instance variables customerID, customerName, address and pinCode. Estimated time: 15 Mins. Step 1: Create a package for the assignment. Step 2: Open Eclipse ganymede IDE and type the following:

/*

* This java file is a demo Java program which depicts a class

* with a main method inside and necessary instance variables

*/

/**

* This class is template to create Customer Object.



* @version 1.0

*/

public class Customer {

private String customerID;

private String customerName;

private String address;

private int pinCode;

/**

* This method creates an object of Customer Class and sets its

*instance variable and display the same.

* @param args The command line arguments

*/

public static void main (String [] args){

Customer customer = new Customer(); //statement 1

customer.customerID = “1234”; //statement 2

customer.customerName = “Jayant”; //statement 3



customer.address = “PHA-Sawan Apts., Yadavgiri, Hyderabad”;

//statement 4

customer.pinCode = 570020; //statement 5

System.out.println(“Customer ID ” + customer.customerID);

System.out.println(“Customer Name ” + customer.customerName);

System.out.println(“Customer Address ” + customer.address);

System.out.println(“Customer Pin Code ” + customer.pinCode);

}

}

Save the file as : Sample.java

Step 2: Compile the program. Read the error reported and fix it (refer to the Note given below).

1. In a java file, if the class is declared as public, the name of the

class and the name of the file should be the same (including the

case).

2. The main() method is the starting point of the program. It is not

mandatory for all the classes to have the main() method. The class

with main() method is called „Starter class‟.

Step 3: Execute the program. Step 4: In the above code main method is a part of Customer class. Step 5: Try to understand the program.

Statement 1: Creates an instance of type Customer and the instance is

assigned to the reference variable “customer”. (More about this on Day 2)

Statement 2…5: Using the reference variable assigning value to the member

variable of the class (similar to structure concept in C)

The following statements retrieve the values assigned to the member

variables and display it.

This exercise is just for demo purpose. The program does not adhere to

the OO concepts.





Creating object of a class

How to access instance variables of an object

Assignment 5: Problem Description to Java Program

CityBank is a multinational private bank. CommunicationTeam employees can open a bank account in CityBank on the day of their joining. Account can be of two types (1) Salary Account and (2) Non Salary Account. For non salary account the minimum bank balance should be Rs 10,000/-. There are different privilege levels (shown in the table below) available on both the accounts.

Type of

customer

Privileges

Salary Non-salary

Multi city cheque book No No

Discount on shopping using

debit card

No Yes

ATM card Yes Yes

The application is used by the clerk of the bank. On allocating it should return a customer id and Account Number. To open a bank account following details are required by the bank: 1 Applicant first, middle and last name 2. Email-id 3. Account Type 4. Date of Birth 5. Gender (M/F) 6. Marital status (Single / Married) Write a program in Java to represent the above description.

Assignment 6: Initializing the class member variables

Modify the above program to get the new account number for the following new employees of CommunicationTeam:



Employee 1: Employee 2:

Name

First: Paul Middle: J Last: Anderson

First: John Middle: Last: Jacob

Date of Birth 3rd Jan,1985 6th March, 1985

Email-id [email protected] [email protected]

Account Type Salary Non-Salary

Gender M M

Marital Status Single Married

Hint: A constructor can be used to initialize class member variables.

Assignment 7: Architectural neutrality of JVM CityBank software is made to be deployed on different architectures. Fill out the below diagram to complete depict the flow of deploying InyBank software which is written in Java.

A .class files

.java files

B1 B2 B3

Q1. What is done in Step A to get .class files?

Q2. .class files are also known as __________? Are the .class files platform independent (Yes/No)?

Q3. Which software is used at B1, B2, B3 to deploy CityBank software? Is the software platform independent (Yes/No)?

Apple

Machine

Windows

Machine

Unix

Machin

e



Assignment 8: Understanding Classes

Problem Description: Create a class to store the employee information and calculate the average feedback and grade based on their feedback. Create the starter class to instantiate the employee and invoke the methods. Estimated time: 15 Mins.

Step 1: Create the class EmployeeGrade according to the below given class diagram.

EmployeeGrade

- employeeNo : int

- employeeName : String

- customer1Feedback: float



- averageFeedback : float

- grade : char

+ initializeEmployee(int employeeNo, String

employeeName, float customer1Feedback, float

customer2Feedback, float customer3Feedback) : void

+ calculateAverageFeedback() : void

+ calculateGrade() : void

+ displayInfo() : void

initializeEmployee(..) : This method initialize employee No, name, feedback

from 3 customers to the member variables. Remember to use „this‟.

calculateAverageFeedback() : This method calculates the average of the 3

feedback and store it in the corresponding member variable.

calculateGrade() : This method calculates the grade for the employee based

on his average feedback. displayInfo(): This method displays the

employeeNo, name, average feedback and the grade of the employee.

Step 2: Save the class under the package of the assignment and compile the program. Fix the

errors, if any.

Step 3: create a starter class with the name City as given below.

Filename City.java

/*

* This java file is a starter class which instantiates EmployeeGrade



* Calls the corresponding methods to initialize the values

* Calculate the average feedback and the grade

* Display the information

*/

/**

* This class is a starter classes that instantiate the EmployeeGrade.

* Using the instance, the class should call the corresponding methods

* to calculate the average feedback and grade.

* Display the information.



* @version 1.0

*/

public class City {

/**

* Instantiate the EmployeeGrade. Set the values for the member

* variables and invoke the method to calculate the average feedback

* and grade. Invoke the method to display the employee information.


*/

public static void main (String[] args) {

// To-do: Create an instance (Elvis) for EmployeeGrade class.

// To-do: Invoke methods for calculating Avg feedback & grade

// To-do: Invoke method to display the employee information

}

}

Save the file as : City.java.

Step 4: Compile City.java. Fix the errors, if any.

Step 5: Execute City.java. Check the output.

The program displays the default value for all the member variables. The

reason being, the main() of the starter class has not invoked the method that

initializes the member variables.

The default constructor for EmployeeGrade has not been defined. Hence the

compiler adds the „default constructor‟ and initializes the variables to the

default value, based on their data type.

Step 6: Modify the main() in City.java to invoke the method that initializes the member

variables, before invoking the method that calculates the average feedback and grade.



Step 7: Compile City.java and execute the program. It should display the information about

the employee.


You have learnt

Initializing the member variables using user-defined methods.

If the constructor is not defined in the program, the system automatically provides

the default constructor and initializes the member variables with default values based

on the data type.

If the member variables are not initialized through the constructor, the programmer

should invoke the method that initializes the member variables, if defined.

Assignment 9: Method Overloading

Problem Description: Create a class to store the employee information and calculate the average feedback and grade based on their feedback. Create the starter class to instantiate the employee and invoke the methods. Estimated time: 15 Mins.

Step 1: Create the class EmployeeGrade according to the below given class diagram.

EmployeeGrade

- employeeNo : int






- grade : char



customer2Feedback, float customer3Feedback) : void



customer2Feedback) : void






initializeEmployee(int employeeNo, String employeeName, float

customer1Feedback, float customer2Feedback, float customer3Feedback)

This method initialize employee No, name, feedback from 3 customers to

the member variables. Remember to use „this‟.

initializeEmployee(int employeeNo, String employeeName, float

customer1Feedback, float customer2Feedback) This method initialize

employee No, name, feedback from 2 customers to the member variables.

Remember to use „this‟.

calculateAverageFeedback() : This method calculates the average of the

available feedback and store it in the corresponding member variable

calculateGrade() : This method calculates the grade for the employee based

on his average feedback. displayInfo(): This method displays the

employeeNo, name, average feedback and the grade of the employee.

Step 2: Save the class under the package of this assignment and compile the program. Fix the

errors, if any.

Step 3: create a starter class with the name City as given below, under the package.

Filename City.java

/*

* This java file is a starter class which instantiates EmployeeGrade

* Calls the corresponding methods to initialize the values



*/

/**







* @version 1.0

*/

public class City {

/**


* variables and invoke the method to calculate the average feedback

* and grade. Invoke the method to display the employee information.


*/




// To-do: Create an instance (Elvis) for EmployeeGrade class.



// To-do: Create an instance (Martha) for EmployeeGrade class.



}

}



Step 5: Execute City.java. Check the output.

Now, open the City.java and modify the program to invoke the method that

initializes the member variables, before invoking the method to calculate the

average feedback and grade, as given in step 6.

Step 6: Call the initializeEmployee method for Elvis as well Martha. All the 3 customers have

given the feedback for Elvis as 4.1, 3,9 and 4.2. But only 2 customers have given the feedback

for Martha as 4.2 and 4.4. Alter the main() method of City.java program as follows.


// To-do: Create an instance (Elvis) for EmployeeGrade class

// To-do: Call the initializeEmployee with 3 feedback



// To-do: Create an instance (Elvis) for EmployeeGrade class

// To-do: Call the initializeEmployee with 2 feedback



}

Step 7: Compile City.java and execute the program. It should display the information about

the employee.




You have learnt

Initializing the member variables using user-defined methods.

If the constructor is not defined in the program, the system automatically provides

the default constructor and initializes the member variables with default values based

on the data type.

If the member variables are not initialized through the constructor, the programmer

should invoke the method that initializes the member variables, if defined.

The methods can be overloaded. If overloaded, the compiler decides the method to

be executed based on the method signature.

Assignment 10: Understanding Constructors

Objective: To understand the usage and the implementation of constructors.

Assignment 10.a: Understanding Constructors

Problem Description: Create a class to store the employee information and calculate the average feedback and grade based on their feedback. Use the constructor to initialize the member variables. Create the starter class to instantiate the employee and invoke the methods. Estimated time: 15 Mins.

Step 1: Create the class EmployeeGrade under the package based on the below given class

diagram.

EmployeeGrade

- employeeNo : int






- grade : char

+ EmployeeGrade()






EmployeeGrade() : This is the default constructor which initializes the

member variables with values as follows.

Employee No :101, Name: “Ram”, customer1Feedback: 4.1f,

customer2Feedback: 4.0f, customer3Feedback: 4.3f

Step 2: Compile EmployeeGrade and fix the errors, if any.

Step 3: Create a starter class with the name City as given below.

Filename City.java

/*

* This java file is a starter class which instantiates EmployeeGrade.



*/

/**







* @version 1.0

*/

public class City {

/**


* variables and invoke the method to calculate the average

* feedback and grade. Invoke the method to display the employee

* information.


*/


// To-do: Create instance(ram) for EmployeeGrade.



}

}





Step 5: Execute City.java. Check the output. It should display the information about

employee 101.

If the default constructor is defined for initializing the values, you need not

explicitly invoke any method to initialize the values.

But when the default constructor is used to initialize the values like shown in

the exercise, every instance is initialized with same values!


You have learnt

Initializing the member variables within default constructor.

If initialized within constructor, need not explicitly invoke any method to initialize.

The same values are initialized to all the instances.

Assignment 10.b: Understanding Constructors

Problem Description: Create a class to store the employee information and calculate the average feedback and grade based on their feedback. Use the constructor to initialize the member variables. Create the starter class to instantiate the employee and invoke the methods. Estimated time: 15 Mins.

Step 1: Make a copy of EmployeeGrade of Assignment 10.a, under the package of this

assignment. Modify the EmployeeGrade according to the below given class diagram.

EmployeeGrade

- employeeNo : int






- grade : char

+ EmployeeGrade()

+ EmployeeGrade(int employeeNo, String


customer2Feedback, float customer3Feedback)






EmployeeGrade() : This is the default constructor which initializes the

member variables to their default values, based on the data type of the

variable.

EmployeeGrade(int employeeNo, String employeeName, float

customer1Feedback, float customer2Feedback, float customer3Feedback)

: This is the overloaded constructor, which initializes the member variables

with the values being passed as parameter.

Step 2: Compile EmployeeGrade and fix the errors, if any.

Step 3: Create a starter class with the name City as given below.

Filename City.java

/*




*/

/**







* @version 1.0

*/

public class City {

/**




* information.


*/


EmployeeGrade ram = new EmployeeGrade();

EmployeeGrade james = new

EmployeeGrade(102,”James”,4.2f,4.4f,4,1f);


for both the employees




for both the employees

}

}

Save the file as : City.java


Step 5: Execute City.java. Analyze the output.


You have learnt

Initializing the member variables within default constructor.

Initializing the member variables using overloaded constructor.

Assignment 10.c: Understanding Constructors

Problem Description: Create a class to store the employee information and calculate the average feedback and the grade based on their feedback. Use the constructor to initialize the member variables. Creating the starter class to instantiate the EmployeeGrade and invoke the methods. - Estimated time: 15 Mins.

Step 1: Make a copy of EmployeeGrade of Assignment 10.b, under the package of this

assignment.

Step 2: Modify the EmployeeGrade.java by commenting the default constructor of the

EmployeeGrade class.

Step 3: Save the program and compile it. Fix the errors, if any.

Step 4: In City.java, comment the instance „ram‟ and all the statements that invoke the

methods through the instance ram.

/*




*/

/**









* @version 1.0

*/

public class City {

/**




* information.


*/


//EmployeeGrade ram = new EmployeeGrade();




for „james‟ alone


for „james‟ alone

}

}

Save the program.

Step 5: Compile the program. Fix the errors, if any

Step 6: Execute the program.


You have learnt

Initializing the member variables using the overloaded constructor, without defining

the default constructor.

Assignment 10.d: Understanding Constructors



Problem Description: Create a class to store the employee information and calculate the average feedback and grade based on their feedback. Use the constructor to initialize the member variables. Creating the starter class to instantiate the employee and invoke the methods. Estimated time: 15 Mins.

Step 1: Make a copy of EmployeeGrade.java and City.java of Assignment 10.c, under the

package of this assignment.

Step 2: Modify City.java by removing the comment for the statement that creates an instance

for „ram‟, as given below.

/*




*/

/**

* This class is a starter class that instantiates the EmployeeGrade.



* Displays the information.



* @version 1.0

*/

public class City {

/**




* information.


*/


EmployeeGrade ram = new EmployeeGrade();




for „James‟ alone




for „James‟ alone

}

}

Save the program.

Step 3: Compile the program. Look into the compilation error and understand the reason.

The compiler would provide the default constructor, only if no other

constructors are defined in the program.

Here, the program has defined the overloaded constructor. So, the system

doesn‟t generate the default constructor. When you try to call the default

constructor, it would throw an error that there is no default constructor.

Remove the comment for the default constructor in the class

EmployeeGrade. Compile the code. Execute City.java


You have learnt

When the parameterized constructors are defined but not the default constructor, if

you try to invoke the default constructor, you would get compilation error.

Assignment 11: Arrays of Objects

Objective: To understand how to create and use arrays of objects.

Problem Description: Create a class that stores information about employees and calculates their grades according to the feedbacks. Use EmployeeGrade class created in Assignment 10.b. Estimated time: 15 Mins.

When the grade is to be determined for just 2 or 3 employees, separate

objects can be created. But what if there are more than 10 or 20 employees.

It is not feasible to create separate objects. That‟s where array of objects is

used.

Step 1: Make a Copy of EmployeeGrade.java from Assignment 10.b under the package of this

assignment.

Step 2: Create City.java under the current package, which creates array of objects for

EmployeeGrade, so that the employee grade can be calculated for any number of employees.



Filename City.java

/*


* Calculates and displays the average feedback and the grade

*/

/**







* @version 1.0

*/

public class City {

/**

* Calculates the average feedback of employees and determines

* the grade.


*/


// create an array of 5 references of EmployeeGrade class

EmployeeGrade [] employee = new EmployeeGrade[5];

// To-do: Initialize the references by calling the

parameterized constructor.

// To-do: Call the corresponding methods to calculate

average feedback and grade for all the 5 employees.

// To-do: Display the details for all the 5 employees

}

}

Save the file as „City.java‟

Step 3: Compile the program. Fix the errors, if any



When an array of objects are created like below,

EmployeeGrade [] employeeGrade=new EmployeeGrade[10];

they are references pointing to null. To create objects, the constructor

should be called on every index of the array as given below, after declaring

the array.

for(int loop=0;loop<employees.length;loop++) {

employeeGrade [loop]=new EmployeeGrade (..); //invokes the overloaded

constructor

}

The above code creates actual objects of the EmployeeGrade class.

Step 4: Execute the program.



To create and use array of objects

---Solve Self Review Questions------------------------------------------------------------------------------


Assignment 12: Static Concepts

Objective: To understand how to create static variables, static blocks and methods and how

to create objects for classes having private constructors, outside the class Problem Description: Create a Loan class for the class diagram shown Estimated time: 15 Mins.

Loan

- loanNo : int

- accountNo : int

- customerNo: int

- loanAmount: float

- loanDuration: int

- interest : float

+Loan()

+Loan(int accountNo , int customerNo,int

loanDuration ,float loanAmount, float interest)

+calculateInstallments() : float

+getAccountNo() : int

+getCustomerno() : int



+getLoanAmount() : float

+getInterest() : float

+getInterest() : float

+setAccountNo(int accountNo) : void

+setCustomerNo(int customerNo) : void

+setLoanDuration(int loanDuration) : void

+setLoanAmount(float loanAmount) : void

+setInterest(float interest) : void

Assignment 12.a: Static Concepts – static variables

Objective: To understand how to create static variables and their usage.

Problem Description: To count the number of instances(Objects created) using static variable Estimated time: 15 Mins.

Step 1: Add a static variable loanCounter to the Loan class.

Step 2: In both the constructors of the loan class add the following statement

Step 3: In the main method of the loan class create some instances of the class loan using

both default and overloaded constructors( may be five or six instances).

Step 4: In the main method of the loan class after creating the instances add the following

statement.

Step 5: Compile and execute the program



How to create static variables

//To count the total number of instances

loanCounter++;

//To print the count of instances created in the main method

System.out.println("Number of instances :"+loanCounter);

//loanCounter counts the total number of objects

static int loanCounter;



Assignment 12.b: Static Concepts - static blocks

Objective: To understand how to use of static blocks.

Problem Description: To count the number of instances (Objects created) using static variable Estimated time: 15 Mins.

Step 1: Now assume that 100 users have already visited the class. Now the count will start from 101. Use static block to initialize the loanCounter variable to 101.

Step 3: In the main method of the loan class create some instances of the class loan using

both default and overloaded constructors ( may be five or six instances).

Step 4: In the main method of the loan class after creating the instances, add the

following statement.

Step 5: Compile and execute the program



How to create static variables

Assignment 12.c: Static Concepts – private constructors and static methods

Objective: To understand static methods to create objects for the class having private

constructors

Problem Description: To create objects of a class having private constructors outside the class Estimated time: 20 Mins.

Step 1: Modify the above class and make the both the constructors as private. Also remove

the main method of the loan class. Create one more class TestLoan.java like this

//To print the count of instances created in the main method

System.out.println("Number of Objects :"+loanCounter);

public class TestLoan {

public static void main(String[] args) {

//To-Do: create the instances of the Loan class

System.out.println("Total number of objects :" +

Loan.loanCounter);

}

}



Step 2: Compile and execute the above class

Above code will not compile as the object of a class cannot be created

outside the class if the constructors are private. Static methods can be used

to create objects for the classes having private constructors

Step 3: Add a static method to the Loan class as shown. Replace the To-Do comments with

the code

Step 4: Modify the TestLoan.java class so that the instances of Loan class are created using

the getLoanInstance() static method .

Step 5: Modify the Loan.java class to make the loanCounter variable as private.

Step 6: Save the Loan class and again compile the TestLoan.java class

Since the loanCounter variable is private now it cannot be accessed outside

the class.

Step 7: Create a method getNumberOfObjects() in the Loan class that will return the

number of objects created of Loan class.

Step 8: Modify the TesLoan.java such that , instead of Loan.loanCounter use

getNumberOfObejcts() method in the SOP statement .

public static Loan getLoanInstance(){

//To-Do: create the object of loan class and return it

}

public class TestLoan {


//To-Do: create the instances of the Loan class using

getInstance() method of Loan class

System.out.println("Total number of objects :" +

Loan.loanCounter);

}

}

public int getNumberOfObjects(){

return loanCounter;

}



Now one thing has to be decided whether to make the getNumberOfObjects()

method as static or not



Static variables and static blocks and their use

Static methods and their use

Assignment 13: Inheritance

Objective: To understand the concept of inheritance

Problem Description: CityBank wants to automate their services to the customers. Bank allows the customers to hold either a Savings Account or Overdraft Account. The account number, customer details, balance for both savings account and the overdraft account should be stored. The customer has to maintain a minimum balance of Rs. 500 in his/her Savings Account. The bank pays an interest of 12% on the balance available in the Savings Account. The bank would fix the overdraft amount for the individuals who possess the Overdraft Account. Hence, the customer who possesses Overdraft Account can withdraw the balance he/she has in their account as well as the overdraft amount fixed for them. Say, if the customer has a balance of Rs. 10000 and the overdraft amount fixed is Rs. 5000, then the customer is eligible to withdraw up to Rs. 15000. The bank wants to automate the deposit, withdraw and the balance enquiry on both the account. The bank also wants to automate the interest calculation for the savings account. Identify the classes to be designed Find the relationship between the classes Identify the member variables and methods of the classes Implement the classes and their methods

Estimated time: 45 Mins.

First three parts of the problem are already implemented in the next section



Assignment 14: Understanding Inheritance

Objective: To understand how to design and implement inheritance.

Problem Description: For the Scenario given as part of Assignment 18, identify, design and implement the various classes. Estimated time: 30 Mins. Step 1: Identify the classes. Identify the classes. Generalization can be applied on Savings

Account and Current Account, which leads to a super class “Account”. All the properties and functionalities that are common to the Savings Account and Current Account would become part of “Account” class. Hence we derive the concept of Inheritance with “Account” being the super class and “SavingsAccount” and “CurrentAccount” being the sub classess. The Account has the

customer details, account number, balance. Hence Customer becomes part of Account class.

Step 2: Design the classes. Below is the class design for Customer and Account.

Customer

- customerId : int

- customerName : String

- customerAddress : String

- pincode : int

+ Customer()

+ Customer(int customerId, String customerName,

String customerAddress, int pincode)

+ setCustomerId(int customerId) : void

+ getCustomerId() : int

+ setCustomerName(String customerName) : void

+ getCustomerName() : String

+ setCustomerAddress(String customerAddress) : void

+ getCustomerAddress() : String

+ setPincode(int pincode) : void

+ getPincode() : int

As you can see the customer is a part of the account class. So customer‟s relation must be shown in the account class. Note the an instance variable of type customer to relate customer to Account class.

Account

- accountNo : int

- customer : Customer



# balance : double

+ Account()

+ Account(int accountNo, Customer customer,

double balance)

+ getCustomer() : Customer

+ balanceEnquiry() : double

+ deposit(double amount) : void

balanceEnquiry(): double

The method returns the balance available in the account.

deposit(double amount): void

The method updates the available balance.

Within all the constructor of all the classes in this assignment, display a

unique message, so that you can understand the execution sequence

of the constructors better.

Step 4: Design the Sub classes.

The SavingsAccount and CurrentAccount would be subclasses for the Account class. The

savings account has minimum balance to be maintained and also provides interest at the rate of

12% to the customers. Current account can no minimum balance limit the balance can go even

negative, but it does not provide any interest rate. Also the account cannot go beyond the

negative balance of 10000

SavingsAccount

- minimumBalance: double

- interestRate: int

+ SavingsAccount()

+ SavingsAccount(int accountNo, Customer

customer, double balance)

+ withdraw(double amount) : void

+ calculateInterest(): void

minimumBalance

Initialize the member variable minimumBalance member variable

with 500.

interestRate

Initialize the member variable to 12

SavingsAccount(int accountNo, Customer customer, double balance)



Call the super class constructor.

withdraw(double amount): void

The method should check whether the account would have the

minimum balance after the withdraw operation. If available, then

update the balance (belonging to Account class). If the sufficient

balance is not available, display an appropriate message.

calculateInterest(): double

The method should calculate the interest for the available balance.

(For simplicity, the interest is calculated for the available balance,

instead of the average of the balance for a period of time)

CurrentAccount

- CurrentAmount: double

CurrentAccount() + CurrentAccount(int accountNo, Customer customer, double balance, double currentAmount) + withdraw(double amount) : void

+ getEligiblityAmount(): double

CurrentAccount(int accountNo, Customer customer, double balance, double currentAmount)

Call the super class constructor and then initializes the currentAmount member variable with the value passed as parameter

withdraw(double amount) The method should check for sufficient balance, by checking whether the amount to be withdrawn is less than or equal to the amount available and the allowed negative amount, the customer is eligible for. If available, withdraw the amount and update the balance. If the sufficient balance is not available, display an appropriate message.For e.g., say if the customer has a balance of Rs. 10000 and he is eligible for negative balance of 10000, then he can withdrew maximum of Rs.20000 (available balance + Eligible Negative amount). If the withdraw amount is Rs. 15000, then the balance available would be – 5000. Then again he is allowed to withdraw 5000 after which his account will show insufficient balance.

getEligiblityAmount(): double The method would return the negative amount the customer is eligible for.

Step 3: Implement the Customer, Account, SavingsAccount and CurrentAccount as per the

design.

Step 4: Implement the starter class. Save the starter class as “CityBank.java”

Filename CityBank.java



/*

* This java file is a starter class which instantiates the Account

* class and call the corresponding methods for various banking

* operations.

*/

/**

* This class is a starter classes that instantiate the Account.

* Using the instance, it invokes the corresponding banking

* operations.


* @author <<Replace with your Employee No. and Name>>

* @version 1.0

*/

public class CityBank {

/**

* Instantiate the Account object. Call the corresponding methods that

* does the various banking operations.


*/


// To-do: Create an instance (john) for Customer class. Call the

overloaded constructor

SavingsAccount johnSA = new SavingsAccount(101,john,1000);

johnSA.deposit(1000);

// To-do: display the balance available in account no 101

// To-do: call the method to withdraw Rs.1600.

// To-do: display the balance available.

// To-do: Create an instance (jenny) for Customer class. Call

the overloaded constructor

OverdraftAccount jennyOA = new

OverdraftAccount(201,jenny,500,2000);

// To-do: deposit Rs. 1500 to the account


Note: available balance for Overdraft Account is

balance+ Allowed negative amount

// To-do: call the method to withdraw Rs. 1000

// To-do: display the balance available





}



}

Step 5: Save and compile all the programs. Fix errors, if any.

Step 6: Execute CityBank. Analyze the outputs.



To identify classes and their relationship (OO Analysis)

To identify data members and methods (OO Design)

To design the classes

To implement the classes

Assignment 15: Understanding Dynamic Binding

Objective: To understand dynamic binding, run-time polymorphism and its usages.

Problem Description: Making the CityBank.java to implement the dynamic binding and run-time polymorphism. Estimated time: 20 Mins.

Step 1: Make a copy of Customer, Account, SavingsAccount, OverdraftAccount and CityBank

of the previous assignment ie. Assignment 14 under the package of this assignment.

Step 2: Modify the CityBank.java as mentioned below (highlighted).

/*


* class and call the corresponding methods for the various banking

* operations.

*/

/**



* operations.


* @author <<Replace with your Employee No. & Name>>

* @version 1.0

*/




/**



* @param args the command line arguments

*/





// To-do: call transaction(johnSA,1000) of CityBank





OverdraftAccount jennyOA = new

OverdraftAccount(201,jenny,500,2000);

// To-do: call transaction(jennyOA,1500) of CityBank


Note: available balance for Current Account is


// To-do: call the method to withdraw Rs. 1000 to A/c No 201

// To-do: display the balance available of 201





}

// To-do: Add the /** .. */ comment for the method

public void transaction(Account account, double amount) {

account.deposit(amount);

}

}

Fix the compilation error in CityBank.java

Step 3: Compile and execute the program. You should get the same output as that of

Assignment 19. Try to understand how the program works.



The compiler, while compiling the program, would find the class for

which the reference variable is declared. The compiler also checks

whether the class has method which is being invoked.

In this case, the account is a reference variable for Account class.

Account class does not have a method withdraw. Hence, the compiler

shows an error within transaction method.

At the time of execution, the run-time environment identifies the

type of the object that the reference variable is pointing to. The run-

time environment invokes the method defined in the class of the

object, the reference variable is pointing to.

In the case of transaction(johnSA,1000), the type of the object that

the reference variable account pointing to is “SavingsAccount”. The

SavingsAccount inherits the deposit method from Account. Hence, the

deposit method in Account would be invoked automatically.

Step 4: Modify the transaction() method of CityBank to call the withdraw() method, as shown

below.

public static void transaction(Account account, double amount) {


account.withdraw(100);

}

Step 5: Compile the program and try to understand the compilation error.

In this case, the account is a reference variable for Account class.

Account class does not have a method withdraw. Hence, the compiler

shows an error.

Step 6: Fix the error, by removing the account.withdraw(100) from transaction method.

Step 7: Compile and execute the program.



The concept of Dynamic binding and run-time polymorphism.

Assignment 16: Understanding Abstract class

Objective: To understand the concept of abstraction (abstract method and abstract class).



Problem Description: Introducing the abstract method and abstract class in CityBank application. Estimated time: 30 Mins.

Step 1: Make a copy of Customer, Account, SavingsAccount, CurrentAccount and CityBank of

the previous assignment i.e., Assignment 15 under the package of this assignment.

Abstract method:

A method can be declared as abstract in the super class, if the

method cannot be defined within the super class, but needs to be

defined within the sub class. By declaring a method abstract, you are

forcing the subclass to define the method.

Abstract class:

A class can be declared as abstract in two circumstances. One, if the

class has any of the method declared as abstract. Other being, If you

don‟t want to instantiate the class but you want to instantiate the

subclass.

Note: Object cannot be instantiated for the abstract class, where as the

reference variable can be declared for the abstract class.

Step 2: In CityBank application, the programmer should not create an object for the class

Account. (In real world, we have either Savings Account or Current Account. There cannot be

simply be an account. Similarly, there is nothing called vehicle existing in the real world. It

would be an instance of car, bike, or other type of vehicles. )

Step 3: Modify the Account class by declaring Account class as abstract.

Step 4: Compile all the programs and execute.

Step 5: Modify CityBank.java as given below.

/*


* class and call the corresponding methods for the various banking

* operations.

*/

/**



* operations.



* @version 1.0

*/




/**




*/




Account account = new Account();







CurrentAccount jennyOA = new

CurrentAccount(201,jenny,500,2000);

// To-do: call transaction(jennyOA,1500) of CityBank


Note: available balance for Current Account is

balance+Allowed negative amount







}




}

}

Step 6: Save and compile the program.

Step 7: Fix the compilation error, by removing the statement highlighted. Compile the

program.



Step 8: Also, as part of OOD, you have identified that the subclasses i.e. SavingsAccount and

CurrentAccount should define the withdraw method. This can be enforced by declaring an

abstract method in the Account class.

Step 9: Modify the Account abstract to have an abstract method with the signature as

follows.

public abstract void withdraw(double amount);

The class should be declared as abstract, if any of the method is

declared as abstract.

Account is already declared as abstract, according to step 3.


Step 11: Try to comment the withdraw method in SavingsAccount and compile the program.

You would get compilation error.

Step 12: Un-comment the withdraw method. Save, compile and execute CityBank.java



Abstract method

Abstract class

Assignment 17: Understanding Dynamic Binding

Objective: To understand and revisit dynamic binding, run-time polymorphism and its usages.

Problem Description: Making the CityBank.java to implement the dynamic binding and run-time polymorphism. Estimated time: 20 Mins.

Step 1: Make a copy of Customer, Account, SavingsAccount and OverdraftAccount of the

previous assignment i.e. Assignment 16 under the package of this assignment.

Step 2: Create a class CityBank, as shown below.

/*


* class and call the corresponding methods for the various bank

* operation.



*/

/**



* operations.



* @version 1.0

*/


/**




*/









CurrentAccount jennyOA = new

CurrentAccount(201,jenny,500,2000);

// To-do: call transaction (jennyOA,1500) of CityBank


Note: available balance for Overdraft Account is


}




account.withdraw(100);

}

}




Now, you are able to call the deposit as well withdraw within

transaction method, because the Account class has the definition of

deposit as well the declaration of withdraw method.




Assignment 18: Understanding Interface

Objective: To understand the concept of interface.

Problem Description: Create classes for different animals like Lion, Hippo, Dog, Cat.

Estimated timed: 20 mts

Step 1: Perform OOA

Step 2: Perform OOD. You should be able to identify the commonality among the nouns.

Hence, you derive at the super class Animal. Dog and Cat again has come commonality as

both are pet animals. Hence you can introduce the concept of generalization here. But, the

Dog and Cat is already inheriting from Animal. Hence PetAnimal cannot be a class.

Make PetAnimal as Interface. The pet animals would have the functionality of being friendly

and playing with the human beings.

Based on these, design the classes, its properties (if any) and functionalities.

Step 3: Implement the Animal, Hippo, Dog, Cat classes and the PetAnimal Interface.

Step 4: Make sure the Dog and Cat are inheriting from both Animal class as well from Pet

interface. Create all the below mentioned classes and interfaces according to the standards.

public interface PetAnimal {

}

public class Animal {

}

public class Hippo extends Animal {



}

public class Dog extends Animal implements PetAnimal {

}

public class Cat extends Animal implements PetAnimal {

}

Step 5: Save all and compile. Execute the program.



The concept of Interface in Inheritance

Assignment 19: Understanding Packages

Objective: To understand the package concept.

Problem Description: Organizing the classes and interfaces of CityBank application into packages. Estimated time: 20 Mins. Note: All package names must start with a lower case letter

Step 1: Create a package with name com.Citybank.customer. Modify the Customer class of

Assignment4, so that it belongs to the package com.Citybank.customer. Make sure the class

and the constructor(s) are declared as public.

Step 2: Compile Customer.java. Fix the errors, if any.

Step 3: Create a package with name com.Citybank.account. Add the Account,

SavingsAccount, CurrentAccount to the package com.Citybank.account. Modify Account class,

so that it imports the Customer class belonging to com.Citybank.customer package. Make

sure all the classes and constructors are declared as public. Otherwise you will not be

able to access the class outside the package.

Step 4: Create a package with name com.Citybank. Add the CityBank to the package

com.Citybank. Make sure the class and constructor(s) are declared as public. Import the

relevant classes and the packages.

Step 5: Compile all the classes and fix the errors, if any.



There won‟t be any error related to locating the package, be it

com.Citybank.customer or com.Citybank.account.

Try to find why the java compiler / run-time do not throw any error.

Step 7: Execute the com.Citybank.CityBank from the package where the package is stored.




Assignment 20: Understanding the Access Specifier

Objective: To understand the concept of Access specifiers.

Problem Description: Create classes in different packages and try to access variables with different access specifiers. Estimated time: 20 Mins.

Step 1: Create a package „package1‟

Step 2: Create two classes Base, Child1 under package1 as given below.

Base.java

package package1;

/*

* This java file is a class which has 4 member variables

* with different access specifiers

*/

/**

* This class is a class that has 4 member variables

* with different access specifiers

* It also has 2 methods to access the variables



* @version 1.0

*/

public class Base {

int variable1;

private int variable2;

protected int variable3;



public int variable4;

/*

* Default Constructor that initializes the member variables

*/

Base () {

variable1=100;

variable2=200;

variable3=300;

variable4=400;

}

/*

* Returns the value of the member variable variable1

*/

int getVariable1(){

return variable1;

}

/*

* Returns the value of the member variable variable2

*/

public int getVariable2(){

return variable2;

}

}

Child1.java

package package1;

/*

* This java file is a class which is a sub class

* of Base class

*/

/**

* This class is a class which extends Base class

* It has a method that gets the values of the

* member variables of Base class



* @version 1.0

*/



public class Child1 extends Base{

public void getValues()

{

System.out.println (getVariable1());

System.out.println (getVariable2());

System.out.println (variable3);


}

}

Step 3: Compile all the classes. Fix the errors.

Members declared without any access specifier is default. They can be

accessed only within the same package

Members declared as private can be accessed only within the class

Members declared as protected can be accessed within the class and also

by sub classes in a different package

Members declared as public can be accessed anywhere

Step 4: Create a package package2

Step 5: Create a class Child2 under package2 as given below.

Child2.java

package package2;

/*

* This java file is a class which is another sub class

* of Base class

*/

import package1.Base;

/**

* This class is a class which extends Base class

* It has a method that gets the values of the

* member variables of Base class



* @version 1.0

*/

public class Child2 extends Base{

public void getValues() {

Base base=new Base();

System.out.println (variable3); // Line 1



System.out.println (base.variable3); // Line 2


}

}

Step 6: Compile Child2.java. Fix the errors.

Though protected members can be accessed in sub classes in different

package, it can be accessed only through inheritance

That is it can be accessed as if it belongs to the same class (Like in

Line 1)

When accessed using an object, it acts as if it is a private variable

(So, Line 2 will throw a compile time error)

Step 7: Compile all the programs and execute the program.



To declare variables with different access specifiers and where it can be accessed.

Assignment 21: Garbage Collection

Objective: To understand the concept of memory allocation and how garbage collection takes

place in Java.

Problem Description: Draw the stack and heap representation for the following class. And identify how many objects are created on heap

Estimated time: 20 Mins.

class Tyre{}

public class Car {

Tyre tyre;

String name;


Car carMain = new Car();

carMain.setFeatures(carMain);

}

void setFeatures(Car car) {

tyre = new Tyre();

car.setName("Swift");

}

void setName(String name){

this.name = name;

}

}



setName() name

setFeatures() car

main() carMain

Overall three objects are created on the Heap.



How memory allocation takes place on heap and stack

Assignment 21a: Garbage Collection


place in Java.

Problem Description: Draw the stack and heap representation for the following class. And identify how many objects will be created on heap


Heap String

Object:

“Swift”

Tyre object

Car object:

Instance variables:

name

tyre

Stack

public class Vehicle {

String vehicleName;

Wheels [] wheels = new Wheels [4] ;


Vehicle vehicle = new Vehicle();

}

}

class Wheels{}




How memory allocation takes place on heap and stack

Assignment 21b: Garbage Collection


place in Java.

Problem Description: Analyze the following code example and tell how many objects will

be garbage collected after

a. Line 1

b. Line 2

c. Line 3

Before solving the above parts of the problem, find the total number of objects that will be

created on heap just before the start of line 1.

Ans :

a. after line 1: 0 Objects will be garbage collected

b. after line 2: 2 Objects will be garbage collected

c. after line 3: remaining 2 Objects will be garbage collected.



To understand the how the stack and heap work together

How to analyze a code to predict the number of objects created on the heap.

public class Garbage {

String garbageLocation;

Garbage garbage;


Garbage garbage1 = new Garbage();

garbage1.garbage = new Garbage();

garbage1.garbageLocation="Hyderabad";

garbage1.garbage.garbageLocation="Kukatpally"; garbage1.garbage.garbage=garbage1;

garbage1.garbage.garbage = null ; //line 1

garbage1.garbage= null; //line 2

garbage1 = null; //line 3

}

}



How to predict the number of objects that are eligible for garbage collection.


Assignment 22: Autoboxing and unboxing

Objective: To understand the autoboxing and unboxing concept.

Problem Description: Write a class to store the list of employee id‟s belonging to a particular project in a vector. Assume that employee from 1001 to 1005 has been assigned a project in CityBank account. Estimated time: 15 Mins.

Step 1: Create a class Employee based on the below given requirements.

/*

* To-do: <<Write appropriate comment>>

*/

/**

* <<Replace with appropriate description>>



* @version 1.0

*/

public class EmployeeInfo{

/**

* To-do: << Replace with appropriate description >>

*/


//Vector is in java.util package. Refer javaDocs

Vector empList = new Vector();

int empNo=1000;

for(int count=0;count<5;count++)

{

empNo++;

// Only object can be added to the vector.

// Convert the int to Integer



// To-do: add the empNo to the vector

}

// To-do: retrieve and display the elements in vector

}

}

Step 2: Complete the above program and execute the same.

Step 3: Modify the above program to use the concept of autoboxing and unboxing, which

would simplify the program. Also, use enhanced for loop to retrieve and display the elements

in the vector.




The concept of Autoboxing and unboxing.

Assignment 23: Understanding Exception Handling (Unchecked Exceptions)

Objective: To understand how to handle the exceptions.

Problem Description: A program that would handle the NullPointerException with try and catch block. Estimated time: 30 Mins.

Step 1: Create a starter class with the name ExceptionHandlingDemo.

Step 2: Write the below given code in the main method of the starter class.

String name;

System.out.println(name.length());

name = "John";


Step 3: Compile the program.

Step 4: Fix the error as shown below.



String name = null;


name = "John";


Step 5: Compile the program.

Step 6: Execute the program and note the exception.

NullPointerException is an unchecked exception. The compiler would

check only for the checked exceptions.

Refer to JavaDoc for further information about

NullPoninterException.

Step 7: Modify the program to handle the run-time exception, as given below.

String name = null;

try{


}

catch(NullPointerException exception){

System.out.println("Object is null");

}

System.out.println(“Continuing the execution...”);

Step 8: Now, execute the program. As the exception raised is handled in the program, the

program does not terminate abruptly, as happened in step 6.

Step 9: Modify the code as given below.

String name = null;

try{


System.out.println(“End of try block”);

}



}


If a statement in the try block, throws an exception, the following

statements in the try block would not be executed.

Hence, System.out.println(“End of try block”); is not executed, when

name.lenght() throws NullPointerException.




Step 11: Modify the code as given below.

String name = null;

int total = 100,count=0;

try{

int average = total/count;

System.out.println(average);


}



}


Step 12: Execute the program and understand the output.

Step 13: Modify the program as given below.

String name = null;


try{




}

catch(ArithmeticException exception) {

System.out.println("Arithmetic Exception " +

exception.getMessage());

}



}


Step 14: Execute and analyze the cause of this output.



The fundamental of exception handling



Assignment 24: Understanding Exception Handling – try, catch & finally

Objective: To understand how to handle the exceptions – try, catch and finally block.

Problem Description: A program that would handle the NullPointerException with try, catch and finally block. Estimated time: 15 Mins.

Step 1: Make a copy of the ExceptionHandlingDemo.java in Assignment 23, under the

package of this assignment.

Step 2: Modify the program as given below.

String name = “john”;


try{




}

catch(ArithmeticException exception) {

System.out.println("Arithmetic Exception " +

exception.getMessage());

}



}

finally{

System.out.println(“within finally block”);

}


Step 3: Compile, execute and analyze the output.

finally block would get executed, even if the try block throws

exception. The finally block should be used to release the resources

that you have locked within the application.

For e.g. you might have opened a file within the try block. It is

always advisable to close the file in the finally block, because the

finally block would be executed definitely irrespective of the

exceptions.

Step 4: Change the value of count to 0. Compile and execute the program. Analyze the

output.



Step 5: Try to analyze the different cases associated with finally block. Especially when the

code in finally will be executed and when it will not.



The fundamental of exception handling (try, catch and finally)

Assignment 25: Understanding Exception Handling (Checked Exceptions)

Objective: To understand how to handle the checked exceptions – try, catch and finally

block.

Problem Description: Write a program that would handle the ClassNotFoundException with try, catch and finally block. Estimated time: 15 Mins.

Step 1: Create a class named ExceptionDemo with the static block given below, under the

package com.exception.

static {

System.out.println(“In the static block of ExceptionDemo..”);

}

Step 2: Create a starter class named CheckedExceptionDemo under the package

com.exception.

Step 3: Make the CheckedExceptionDemo program to load the ExceptionDemo class at run-

time.

class Class has a method named “forName”, which loads any given

class at run-time.

public static void main(String arg[]) {

Class.forName(“com.exception.ExceptionDemo”);

}

Step 4: Save and compile the program.



The compiler throws an exception in Class.forName(..). The forName

method of Class, throws checked exception –

ClassNotFoundException. The compiler expects the programmer to

handle the checked exception.

Step 5: Modify the method as shown below.

public static void main(String arg[]) {

try{

Class.forName(“com.exception.ExceptionDemo”);

}

catch(ClassNotFoundException exception){

System.out.println(“Exception : “ + exception);

}

}


To get to know about whether the method throws any checked

exception, refer to the java doc. All those methods mentioned in the

throws clause of the method signature are checked exceptions.

E.g. refer to the method signature of forName of Class.



To handle the checked exceptions

Assignment 26: Understanding User defined Exception Handling

Objective: To understand how to handle the user-defined exceptions.

Problem Description: The withdrawal method of SavingsAccount and OverdraftAccount should raise an exception, if the balance is not sufficient for withdrawl. Estimated time: 15 Mins.

Step 1: Make a copy of Account, SavingsAccount, CurrentAccount and CityBank programs from

Assignments of Day 2 under the package of this assignment.

Step 2: Create User defined exception class, InsufficientBalanceException, as shown below.

/*



* To-do: <<Write appropriate comment>>

*/

/**

* <<Replace with appropriate description>>



* @version 1.0

*/

public class InsufficientBalanceExcpetion extends Exception {

/**

* To-do: << Replace with appropriate description >>

*/

public InsufficientBalanceException(){

super("Sufficient Balance not available");

}

}

Step 3: Modify the withdraw method of both SavingsAccount as well OverdraftAccount to

throw the exception

public void withdraw(double amount) throws

InsufficientBalanceException {

// logic to check the sufficient balance

// if (availablebalance <= amount)

throw new InsufficientBalanceException();

// else

// Update the balance

}

Step 4: Modify the CityBank program to handle the exceptions.

try {

// johnSA.withdraw(amount);

// johnSA.

} catch (InsufficientBalanceException e) {

System.out.println(e.getMessage());

}

Step 5: Similarly modify the code every time you invoke the withdraw method.

Step 6: Compile all the programs and execute it.





To handle the user defined exceptions

To handle the exception


Assignment 27: JavaBeans

Objective: To understand how to create JavaBeans using Eclipse IDE.

Problem Description: Create a EmployeeBean class named Employee under the package of

this assignment. Employee should contains following fields:

Step 1: select all the fields and right click, you will get a floating menu.

Step 2: From the floating menu select source and then select Generate Getters and Setters

and the same are highlighted in the screenshot above. After you select, you will get a window

like this.

public class Employee{

int employeeID;

String employeeName;

Calendar dateOfBirth;

}



Step 3: select the checkboxes for the fields for which you want to generate the getters and

setters. From the right you can select different options of generating only setters or getters.

Then click ok.

Step 4: Save and compile the bean class



How to create JavaBeans using Eclipse IDE

Assignment 28: Creating (Java Bean) Classes and Object

Objective: To understand what is java bean and how to create a java bean class and

instantiate it in another class. Problem Description: Create a Customer (Bean) class with instance variables customerID, customerName, address and pinCode. Create another starter class and instantiate Customer bean object in it. Estimated time: 15 Mins.



Step 1: Create a Java Bean Class – Customer according to the below given class diagram. Save

the file as Customer.java under the package of the assignment.

Customer

- customerId : int



- pincode : int

+ setCustomerId(int custId) : void


+ setCustomerName(String custName) : void


+ setCustomerAddress(String custAddress) : void


+ setPincode(int pin) : void


Java Bean:- Java Bean is defined as a reusable component. A java bean class

should adhere to the following rules.

All the member variables should be declared private

(Almost) All the member variables should have the Getter and Setter

methods

o Setter Method is to set the value for the corresponding

member variable.

o Getter Method is to retrieve the value stored in the

corresponding member variable.

Name of the Getter & Setter method should match the variable name

o E.g, member variable : customerName (according to the java

naming convention the variable should follow camel-casing.

Hence first letter should be in lower case)

Setter Method Name : setCustomerName

Constructor need not be defined

Step 2: Create a starter class with name “CityBank”.

Filename CityBank.java

/*

* This java file is a starter class which instantiates Customer bean

* and call the corresponding setter (to assign values) and getter

* methods (to retrieve the values and display it)from the main method

*/

/**

* This class is a starter classes that instantiate the Customer bean.



* Using the instance, it calls the setter to set the member variables

* and the getter method to display the values



* @version 1.0

*/


/**

* Instantiate the Customer bean. Set the values for the member

* variables and get the values and display the same.


*/


// To-do: Create an instance (john) for Customer class.

//Set the values of all the member variables for „john‟

john.customerId = 101;

//To-do: Set the values for all the other member variables

// Retrieve the values and display it

System.out.println(john.customerId);

//To-do: Retrieve and display all the other member variables

}

}

Step 3: Try to Compile the CityBank.java. Read the compilation error and try to fix it.

The java compiler would list compilation errors like “customerId has

private access in Customer” for customerId and similar error for

other member variables. If those compilation errors are not listed,

then the Customer class has not been created according to the class

diagram. Check whether all the member variables are declared as

„private‟. Modify Customer.java accordingly and recompile the code.

The customerId is private in Customer class. The private members

can be accessed only within the class. According to the OO concept

(refer to encapsulation and data hiding concept in the slide), the

member variables cannot be declared as public. The only way to

access the member variable is through the setter and getter

methods.

Step 4: Modify the CityBank.java accordingly.



Use john.setCustomerId(101) – to set the value for the member

variable

Use john.getCustomerid() – to retrieve the value and display the same

in CityBank

Similarly, call the corresponding methods of all the member variables.

Step 5: Save the program. Compile it. Fix all the errors, if any.

Step 6: Execute the CityBank class and check the output.



Java Beans

Creating object of one class in another class

How to access member variables of an object

Assignment 29: Usage of ‘this’ keyword

Objective: To understand the usage of „this‟ keyword. Problem Description: Create a Customer (Bean) class with instance variables customerID, customerName, address and pinCode and use the „this‟ to represent the current object within the member methods. Estimated time: 15 Mins.

Step 1: Make a copy of Customer.java and CityBank.java of Assignment 28, under the package

of this assignment.

Step 2: Alter the class according to the below given class diagram.

Customer

- customerId : int



- pincode : int

+ setCustomerId(int customerId) : void


+ setCustomerName(String customerName) : void


+ setCustomerAddress(String customerAddress) : void




+ setPincode(int pincode) : void


The parameter name of the setter methods is different from

Assignment 8. You have to change the variable name used within the

setter methods to match the member variable names.

e.g. public void setCustomerId(int customerId) {

customerId = customerId;

}

Step 3: Compile Customer.java. Fix the errors if any.

Step 4: Compile CityBank.java and fix the errors if any.

Step 5: Execute CityBank.java.

Do you get the default value for all the properties? Try to analyze the

output

public void setCustomerId(int customerId) {

customerId = customerId;

}

The value of the local variable customerId is assigned to the local

variable itself, instead of the member variable customerId.

Step 6: Do the necessary modification in the Customer class, so that the values get initialized

to the member variables rather than the local variables themselves.

Alter the setter definition in Customer as follows.

public void setCustomerId(int customerId) {

this.customerId = customerId;

}

this.customerId, „this‟ – refers to the current object i.e. john. Hence

the value of the local variable customerId is assigned to john‟s

customerId. Similarly change the definition for all the setter methods.

Step 7: Compile Customer.java. Fix the errors, if any.

Step 8: Execute CityBank. Check whether the program displays the Customer Id, Name,

address and pincode of john.


You have learnt

Usage of „this‟



Assignment 30: Understanding Collection Framework

Objective: To understand the Collection framework.

Problem Description: A program to store the employee object in the ArrayList. Estimated time: 20 Mins.

Step 1: Create a EmployeeBean class named Employee under the package of this assignment.

Employee contains following fields:

Note: you can use the EmployeeBean created as a part of earlier assignment.

Step 2: Create a starter class named EmployeeInfo under the package of this assignment as

shown below.

Step 3: Change the class to retrieve the records using forEach loop not an iterator



Basics of the collection framework using ArrayList and List.

Assignment 31: Reflection API

Objective: To understand the basics of reflection API.

int employeeID;

String employeeName;

Calendar dateOfBirth;

public class EmployeeInfo {


//To-Do : create four employee objects

//To-Do : store the objects in the ArrayList

/* [ HINT :]

* Employee employee1 = new Emlpoyee();

* employee1.employeeID = 1001 ;

* List list = new ArrayList();

* list.add(employee1);

*/

//To-Do : retrieve the employee objects from the list using iterator

and display their information

}

}



Problem Description: To analyze a class using Reflection API Estimated time: 20 Mins.

Step 1: Copy the class file of the Employee bean in the current package of this assignment.

Step 2: Create a TestReflection.java in the current package of the assignment. Class will look

something like this.

When you will save (+compile) the file. You will get a checked

exception ClassNotFoundException because the Class.forName() is a

static method which throws ClassNotFoundException.

Step 3: Make the above code compile, put the above code in the main in try-catch block or

use throws clause with the main.

Step 4: Replace the comments with actual code that is required to collect information about

the fields and methods in the Employee class.



How to use Reflection API

import java.lang.reflect.*;

public class TestReflection {


Class classObj = Class.forName("Employee");

}

}

try {

Class classObj = Class.forName("Employee");

//To-Do : write code to collect the method information- name and

parameters

// To-Do : write code to collect field information -access

specifiers and data types

} catch (ClassNotFoundException e) {

e.printStackTrace();

}



Assignment 32: Annotations

Objective: To understand the basics of reflection API.

Problem Description: Use @Deprecated annotation to make the function of a class deprecated. Estimated time: 15 Mins.

Step 1: Create a java class as shown below

Step 2: Create a java class to test the above class as shown below

public class StringMock {

String capacity;

public StringMock(){

}

public StringMock(String capacity){

this.capacity=capacity;

}

/** Description: method returns the position of the character if

* char to be searched is present in the String otherwise it

* returns -1

* @param string

* @param searchItem

* @return int

*/

@Deprecated

public static int search(String string,char searchItem){

//declare loop variable

int index ;

//convert the string to char array

char [] charArray = string.toCharArray();

//iterate over the char array to search for the character

for(index=0; index < charArray.length; index ++){

if(charArray[index]==searchItem) return index;

}

return -1 ;

}

}

public class TestStringMock {


String message = "What's in the name";

//To-Do : create an object of StringMock class

//To-Do : Use search method to search for a character present

in the array

//To-Do : Use search method to search for a character not

present in the array

}

}



You will see that the method with which you gave @Deprecated

annotation will come as deprecated when you are using it. Likewise

fields and even class can be made as deprecated



Basics of built-in annotations

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