Xii Important Questions With Solution Informatics Practices

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XII Informatics Practices 2013 important questions with solution

1. Why do you use import statement in java programming? Explain with example.

Ans. The import statement in Java allows programmers to refer to classes which are declared in other

packages to be accessed without referring to the full package name. Import statement must be the first

line of the program. Import statement have 2 option for importing the classes from packages

a. single class from package by mentioning the class name specifically. Eg. import

javax.swing.jOptionPane;

b. entire class by using * (asterisk) symbol in place of class name. Eg. import javax.swing.*;

Classes from the java.lang package are automatically imported, so it is not require to explicitly

importing.

2. What will be the initial value of an object reference which is defined as an instance variable?

Ans. Each instance variable is initialized with a default value when it is created:Type Initial / Default value Type Initial / Default value

byte 0(Zero of byte type) double 0.0D

short 0(Zero of byte type) char null character i.e., \u000

int 0 boolean false

long 0L All reference types null

float 0.0F

3. What is the purpose of if statement? Describe the different forms of if statements with example.

Ans. An if-statement tests a particular condition; if the condition evaluates to true, a statement or set of

statements is executed otherwise the statement or set of statements is not executed.

There are four different forms of if statements which are as following:1. Simple if statement: Example:

if(ch== )

label1.setText(It is space character);

2. If-else statement: Example:

if(num>0)

label1.setText(number is positive);

else

label1.setText(number is negative or zero);

3. Nested if statement:

if(num>0)

{

if(num


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method is called a local variable.

2. Global variable: If a variable is declare outside all methods, then its scope includes all the

methods and it is said to be a global variable.

5. What do you understand about inheritance? Write the advantage of inheritance.

Ans. Inheritance is a form of software reusability in which new classes are created from existing classes by

absorbing their attributes and behaviors.

Advantages:

Inheritance is capable of expressing the inheritance relationship of real world models. Men

inherit from person; woman inherits from person etc.

Inheritance facilitates the code reusability. Additional features can be added to a class by

deriving a class from it and then by adding new features to it. Class once written and tested

need not be re-written or re-defined.

Inheritance is capable of simulating the transitive nature of real worlds inheritance, which in turn saves

on modification time and efforts, if required.

6. Difference between if-else and switch-case.

Ans. if-else switch-caseIf can evaluate a relational or logical expression

i.e., multiple conditions.

Switch can only test for equality.

The if-else constructions lets you use a series of

expressions that may involve unrelated variables

and complex expression.

The switch statement selects its branches by

testing the value of same variable.

The if-else statement can handle floating point

test also a part from handling integer and

character tests.

A switch cannot handle floating point tests. The

case labels of switch must be an integer byte,

short, int or a char.

7. Difference between while and do-while.

Ans. while do-whileWhile is an entry-controlled loop. do-while is a exit-controlled loop.

In while loop the test expression is evaluated at

the end of the loop i.e., after executing the loop

body.

In do-while loop the test expression is evaluated

at the beginning of the loop i.e., before executing

the loop body.

Syntax:

while(test-expression)

{

// statement

}

Syntax:

do

{

// statement

} while(test-expression);

8. What are the steps required to execute a query in JBDC?Ans. 1. Import the packages required for database programming.

2. Register the JDBC Driver.

3. Open a connection.

4. Execute a query.

5. Extract data from result set.

6. Clean up the environment.

9. List the Advantages of JDBC.

Ans. Provide Existing Enterprise Data

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Simplified Enterprise Development

Zero Configuration for Network Computers

Full Access to Metadata

No Installation

Database Connection Identified by URL

10. Difference between JTextField and j PasswordField.

Ans. When we type text into a JTextField control, it shows the characters in the control, but in

JPasswordField control the typed characters are shown as astriks for security.

11. Differentiate between Java and NetBeans. What is IDE?

Ans. Java is both a programming language and a platform whereas NetBeans is a free, open source,

cross-paltform IDE with built in support for java programming language.

IDE: Integrated Devlopment Envirnment(IDE), its a software tool to help programmer to edit

source code, compile, interpreate and debug.

12. What is ByteCode. Explain JVM.

Ans. ByteCode: A bytecode is a byte-long instruction that the Java compiler generates and the Java

interpreater executes.JVM: JVM(Java Virtual Machine) is a program which behaves as interpreter and translate bytecode into

machine languages as they go- called just-in-time compilation(JIT).

13. Differentiate between ODBC and JDBC driver.

Ans.

ODBC JDBC

odbc is open database connectivity. jdbc is java database connectivity.

OBDC is for Microsoft. JDBC is for Java applications.

ODBC mixes simple and advanced

features together and has complex

options for simple queries.

JDBC is designed to keep things simple

while allowing advanced capabilities

when required. ODBC requires manual installation of the

ODBC driver manager and driver on all

client machines.

JDBC drivers are written in Java and JDBC

code is automatically installable, secure,

and portable on all platforms.

14. Differentiate between Call by Value and Call by Reference.

Ans. Call By Value Call by reference

Call by value is used to create a temporary copy

of the data which is transferred from the actual

parameter in the final parameter.

Call by reference is used to share the same

memory location for actual and formal

parameters

The changes done in the function in formal

parameter are not reflected back in the callingenvironment.

The changes done in the function are reflected

back in the calling environment.

It does not use & sign It makes the use of the & sign as the reference

operator.

15. What are containers or container controls?

Ans. A containers are a controls that can hold other controls within it e.g., a Frame(there can be multiple

controls inside a frame) or a label(it can hold an image and/or text) or simply window (we can put so

many controls on it). Controls inside a container are known as child controls. The child controls can

exist completely inside their containers. That means we cans move them outside their container.



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When we delete a container control, all its child controls automatically get deleted.

16. What is a list? How is it different from combo box?

Ans. A List is a graphical control that displays a list of items in a box wherefrom the user can make

selections

Difference between List and ComboBox

List ComboBox

A list doesnt have a text field the user can

used to edit the selected item.

A combobox is a cross between a text field

and a list.

In a list, the user must select items directly

from the list.

In a combobox user can edit it if he/she

whishes.

The list doesnt drop down. A combobox takes less space initially but

drops down when user clicks on its arrow.

Lists allow us to select more than one item. Combobox allows only single item

selection.

17. What do you mean by life time of variable? How is a local variable different from other variable?

Ans. The lifetime of variable is the period during which it can be accessed.

A local variable is declared inside a method and is accessible only inside that method. In this

way local variable is different from other variable.

18. What is the purpose of default clause in a switch statement?

Ans. Default is used for the else situation. The default statement gets executed when no match is found.

19. While working in NetBeans, Raj included a Listbox in the form. Now she wants the list of her friend's

names to be displayed in it. Which property of Listbox control should she use to do this?

Ans. Modal property

20. What is constructor? How can you call access super class constructor from sub class.

Ans. Constructor: A member method with the same name as its class is called constructor and it is used to

initialize the objects of that class type with a legal initial value.By using super keyword we can call access super class constructor from sub class.

21. Ms. Samhita has developed a Java application through which the students of her school can view

their marks by entering their admission number. The marks are displayed in various text fields. What

should she do so that the students are able to view but not change their marks in text fields?

Ans. By uncheck editable property of JTextField.

22. What is the purpose of break statement in a loop?

Ans. The break statement is used to break from an enclosing do, while, for, or switch statement. Break

breaks the loop without executing the rest of the statements in the block.

23. What is the use of super keyword?

Ans. The first use of keyword super is to access the hidden data variables of the super class hidden bythe subclass.

The second use of the keyword super in java is to call super class constructor in the subclass.

24. What are the 3 types of error found in program? Explain them briefly.

Ans. 1. Compile-Time Errors

Compile-time errors (syntax errors and semantics errors) refer to the errors that violate the

grammatical rules and regulations of a programming language.

2. Run-Time Errors

Run-time errors occur during the execution of a program.



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3. Logical Errors

Logical errors occur due to mistaken analysis of the problem.

25. What should be done so that only one of the radio buttons (Male and Female) can be selected at a

time?

Ans. We should use ButtonGroup component so that only one of the radio buttons (Male and Female) can

be selected at a time.

26. A phone number, consisting of 10 digits, is stored in a string variable strPhone. Now it is required to

store this phone number in a Long type variable lngPhone. Write a Java statement to do this.

Ans. String strPhone = "123456789";

long lngPhone = Long.parseLong(strPhone);

System.out.println(lngPhone);

27. Write a java method to fetch the data from the employee table and display it in jTable the method

already having Connection class object name con, Statement class Object name smt and ResultSet

class object rs with the following query

SELECT EMPNO, ENAME, JOB, SAL FROM EMP.

Ans. import java.sql.*;import javax.swing.table.*;

import javax.swing.JOptionPane.*;

// button

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {

// TODO add your handling code here:

DefaultTableModel model=(DefaultTableModel)jTable1.getModel();

int rows=model.getRowCount();

if(rows>0)

{

for(int i=0;i


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System.out.println(no+"|"+name+"|"+job1+"|"+salary);

model.addRow(new Object[]{no,name,job1,salary});

}

}catch(Exception e)

{ }

}

28. What is abstract method? Write a Java code to demonstrate abstract method.

Ans. An abstract method is a method that is declared without an implementation (without braces, and

followed by a semicolon). If a class includes abstract methods, the class itself must be declared abstract

Example:

Public abstract class Shape

{

String name;

double area;

public abstract void display();}

Class Circle extend shape

{

double radius;

double calcArea()

{

return 3.154 * radius * radius;

}

public void display()

{

System.out.println(radius= + radius);

System.out.println(area= + calcArea());

}

}

29. What is Package? Explain various built-in packages of Java.

Ans. Package: A package is a Java language element used to group related classes under a common name.

java.lang: Provides classes that are fundamental to the design of the Java programming

language. The most important classes are Object, which is the root of the class hierarchy, and

Class, instances of which represent classes at run time.

java.util: Contains the collections framework, legacy collection classes, event model, date and

time facilities, internationalization, and miscellaneous utility classes (a string tokenizer, arandom-number generator, and a bit array).

30. What is Interface? Write syntax of Interface and implementation of Interface.

Ans. Interface: Interface is similar to a class which may contain methods signature only but not bodies and it

is a formal set of method and constant declarations that must be defined by the class that implements

it.

Syntax of Interface:

interface interface_name {

Interface_body



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}

Syntax of implementation of Interface:

class class_name implements interface_1, interface_2,. {

Interface_body

}

31. Which method converts a string to an integer?

Ans. parseInt()method converts a string to an integer.

32. Write a method in Java that takes two integer arguments and returns power of it. Suppose x and y

passing as an argument then it returns x to power y after calculation.

Ans. int cal_power(int x, int y)

{

int x=Math.pow(x,y);

return(x);

}

33. Write a Method in Java to take a number as argument and print the product of its digit, as if a

number entered is 234 then the program gives o/p as 24.Ans. import java.io.*;

public class JavaApplication6 {

public static void main(String[] args)

{

int n, r = 0;

int a=1;

try{

BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

System.out.println("Enter the number");

n=Integer.parseInt(br.readLine());while( n != 0 )

{

r=n%10;

a=a*(r);

n=n/10;

}

System.out.println(" No is=\n "+a);

}catch(Exception e)

{}

}

}

34. Write the Java Code for Finding Prime No.

Ans. class prime

{

public static void main(String p[])

{



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int i,j,s=0,d=0;

for(i=1;i


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public class JavaApplication14

{

public static void main(String[] args)

{

int n, reverse = 0;

try{


System.out.println("Enter the number");

n=Integer.parseInt(br.readLine());

while( n != 0 )

{

reverse = reverse * 10;

reverse = reverse + n%10;

n = n/10;

}

System.out.println("Reverce No is=\n "+reverse);}catch(Exception e)

{}

}

}

37. Write the Java Code for Fibonacci Series.

Ans. import java.io.*;

class Fibonacci{

public static void main(String args[])

{

int n=10,first=0,second=1,next,c;

try{


System.out.println("Enter the number of terms ");

n=Integer.parseInt(br.readLine());

System.out.println("First terms of fibonacci series are :-\n"+n);

for(c=0;c


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}

38. Write Factorial () function and pass an integer number as a argument and return a factorial of passed

number by using recursion method.

Ans. import java.io.*;

class Factorial

{

long fact(long a)

{

if(a


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g. getInstance()

h. setSize()

i. getSelectedValue()

j. executeUpdate()

k. getPassword()

l. getSelectedItem()

m. addItem()

n. append()

o. setVisible()

p. createStatement()

q. setEnabled()

r. setEitable()

Ans. a. getString() : getString() method is provided by ResultSet object and used for obtaining column

data for a row.

Example: String st=rs.getString(ABC);

b. substring(): this method is used to return a part or substring of the String used to invoke themethod. The first argument represents the starting location of the substring.

Example: String s=abcdefghi;

System.out.println(s.substring(5));

System.out.println(s.substring(5,8));

c. length(): This method count and return the number of characters contained in the string object.

Example: String str=Informatics Practices;

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

d. capacity(): Returns the current capacity. The capacity is the amount of storage available for

newly inserted characters, beyond which an allocation will occur.

Example: String str=Informatics Practices;

System.out.println(str. capacity());

e. round() : Rounds to the nearest integer. So, if the value is more than half way towards the

higher integer, the value is rounded up to the next integer.

Example: Math.round(1.01);

f. isSelected(): This is a JCheckBox and JRadioButton method which return the state of the button.

True if the toggle button is selected, false if its not.

Example: if(JRadioButton1.isSelected()==true)

{

JLable1.setText(selected);

}

else{

JLable1.setText( not selected);

}

g. getInstance(): This method is used to get the instance of a object.

Example: class abc

{

abc ab;

ab.getInstance();



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}

h. setSize(): setSize() is used for setting a size for JFrame.

Example: Jframe1.setSize(100,100);

i. getSelectedValue(): Returns the selected value when only a single item is selected in the list.

When multiple items are selected, it returns the first selected value. Returns null if there is no

selection.

Example: String dur=(String)jList1.getSelectedValue();

jLabel1.setText(dur);

j. executeUpdate(): Execute the given SQL statement, which may be an INSERT, UPDATE or

DELETE statement or SQL statement that returns nothing, such as SQL DDL statement.

Example: String sql=DELETE FROM Employees;

ResultSet rs=stmt. executeUpdate(sql);

k. getPassword():getPassword()method is used to obtain password from a password field.

Example: String ped=new String(pwdfld.getPassword());

l. getSelectedItem(): Returns the selected item.

Example: String dur=(String)jComboBox1.getSelectedItem();jLabel1.setText(dur);

m. addItem(): Adds an item to the item list, in the end, of the combo box.

Example: citycb.addItem(ABC);

n. append(): Adds the specified text to the end of the text area.

Example: jTextArea1.append("ABC");

o. setVisible(): Makes the check box visible if true is passed otherwise hides the check box.

Example:jchackBox1.setVisible(true);

p. createStatement(): Creates a SQL statement object for building and submitting an SQL

statement to the database.

Example: Statement stmt = con.createStatement( );

q. setEnabled(): Enables the check box if true is passed otherwise disable the check box.

Example:jchackBox1.setEnabled(true);

r. setEditable(): Sets whether the user can edit the text in the Text Field. Default is true.

Example: NameTF.setEditable(True);

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Xii Important Questions With Solution Informatics Practices

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