Post on 24-Mar-2020
Tutorial 1
Agenda
Laboratory 1
Assignment 1
Installing Eclipse
A problem solved using Eclipse
Arithmetic expression and Assignments
Conditions
Lab 1
Your first JAVA Application
• Objectives of this first Lab is to:
– Learn how to write a simple JAVA
application
– Compile and run a JAVA application
In this laboratory you have to write a JAVA
application that finds a prime number.
Remember! A number is a prime number if it can
be divided only by 1 and itself.
Examples:
37 is a prime
35 is not a prime
Laboratory 1
Work to be done a) Your Java program includes the value of a
number called, say numberSupplied.
b) Your program then must compute and print
the first prime number greater than
numberSupplied.
Example 1
If numberSupplied is 20, your program
should print the first prime number greater
than 20. The following message must be
printed:
The first prime number greater than 20 is 23
Work to be done(Cont’d)
Example 2
If numberSupplied is 44, your program
should print the first prime number greater
than 44. The following message must be
printed:
The first prime number greater than 44 is 47
Tasks to be performed
a) Compute the first prime number greater
than numberSupplied
b) Display the results to the user.
Assignment 1 You have to write an application in Java to solve the
following problem.
• In cryptarithmetic puzzles, mathematical equations are
written using letters. Each letter corresponds to a digit
from 0 to 9 but no two letters can be the same. Here is a
sample problem:
SEND + MORE = MONEY
• A solution to the puzzle is S = 9, R = 8, O = 0, M = 1, Y =
2, E = 5, N = 6 and D = 7.
S E N D 9 5 6 7
M O R E 1 0 8 5
M O N E Y 1 0 6 5 2
Assignment 1 (Cont’d)
• Write a program that finds a solution to the
puzzle of
TOO + TOO + TOO + TOO = GOOD
TOO
TOO
TOO
TOO
GOOD
Assignment 1(Cont’d) Idea:
1) Use a nested loop for each letter used in the puzzle (T, O, G and
D).
2) The loops would systematically assign the digits from 0 to 9 to
each letter.
3) Exclude those combinations of values of T, O, G, D where the
same digit is assigned to more than one letter.
4) Check if all conditions are satisfied. If so display the values
assigned to T, O, G, D.
Installing Eclipse
• Download JDK from the oracle website.
• Set the path properly
• Download eclipse from eclipse.org
• Unzip it and put the eclipse directory under
the root directory.
• create a short cut for eclipse on your
desktop.
Steps to remember Step 1) start eclipse
Step 2) Start a workspace. I selected 212_Fall14 a directory I had
created to hold all my work for this term.
Step 3) Create a new java project. I called mine LabAssign1. This will
include both my lab and my assignment for this week.
Step 4) In the package explorer, under this project, you will see src
(standing for source). Select it.
Step 5) Create a new package. This is a directory under which your java
class definitions will be stored. I called my package aPackage.
Step 6) Create a new class file. This will contain your java source code.
At this point we are only creating Java applications. So give a name to
your class (for example Lab1) and select the method stub main.
See next slide for what you get.
Resulting file package aPackage;
public class Lab1 {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
}
}
Code after typing one line
package aPackage;
public class HelloWorld {
/**
* @param args
*/
public static void main(String[] args) {
System.out.println("Hello How are you?");
}
}
Select Run -> Run As -> 1 Java application
Use of meaningful variable names
Good indentation rules
Adequate documentation is essential.
Look at the Java coding conventions I
have posted on the web.
A problem to solve
• You wish to purchase a car for $25000. You
are making monthly payments of $1000. The
interest rate is 1% per month, calculated
monthly.
• Display a table showing how much you pay
every month and the remaining loan amount.
Ideas:
Initial balance = $25000.00
At the end of the first month,
i) interest due = $250.00
ii) current balance before payment = $25250.00
iii) payment made = 1000.00
iv) current balance after payment = $24250.00
At the end of the second month,
i) interest due = $242.50
ii) current balance before payment = $24492.50
iii) payment made = 1000.00
iv) current balance after payment = $23492.50
And so on until the loan is paid off.
( I have deliberately glossed over some details)
Initialize the value of current balance and interest rate.
While (loan is not paid off)
i) calculate interest on current balance
ii) calculate payment amount.
iii) calculate new balance after payment.
iv) display month payment is made and the new balance.
public class CarLoan {
public static void main(String a[]){
Initialize the value of current balance and interest rate.
While (loan is not paid off)
i) calculate interest on current balance
ii) calculate payment amount.
iii) calculate new balance after payment.
iv) display month payment is made and
the new balance.
}
}
public class CarLoan {
public static void main(String a[]){
double currentBalance, interestRate, interestPayment,
paymentMade;
int month = 0;
currentBalance = 25000.00;
interestRate = 0.01;
while (currentBalance > 0.0) {
month ++;
interestPayment = currentBalance * interestRate;
paymentMade = 1000.00;
currentBalance = interestPayment + currentBalance - paymentMade;
System.out.printf("Month %3d\t Payment $%8.2f New Balance $%8.2f\n",
month, paymentMade, currentBalance);
}
}
}
Month 1 Payment $ 1000.00 New Balance $24250.00
Month 2 Payment $ 1000.00 New Balance $23492.50
Month 3 Payment $ 1000.00 New Balance $22727.43
Month 4 Payment $ 1000.00 New Balance $21954.70
Month 5 Payment $ 1000.00 New Balance $21174.25
Month 6 Payment $ 1000.00 New Balance $20385.99
Month 7 Payment $ 1000.00 New Balance $19589.85
Month 8 Payment $ 1000.00 New Balance $18785.75
Month 9 Payment $ 1000.00 New Balance $17973.60
Month 10 Payment $ 1000.00 New Balance $17153.34
…….
Month 25 Payment $ 1000.00 New Balance $ 3817.60
Month 26 Payment $ 1000.00 New Balance $ 2855.78
Month 27 Payment $ 1000.00 New Balance $ 1884.33
Month 28 Payment $ 1000.00 New Balance $ 903.18
Month 29 Payment $ 1000.00 New Balance $ -87.79
What is
the
problem?
public class CarLoan {
public static void main(String a[]){
double currentBalance, interestRate, interestPayment, paymentMade;
int month = 0;
currentBalance = 25000.00;
interestRate = 0.01;
while (currentBalance > 0.0) {
month ++;
interestPayment = currentBalance * interestRate;
if (interestPayment + currentBalance >= 1000.00){
paymentMade = 1000.00;
currentBalance = interestPayment + currentBalance – paymentMade;
} else {
paymentMade = interestPayment + currentBalance;
currentBalance = 0.0;
}
System.out.printf("Month %3d\t Payment $%8.2f New Balance $%8.2f\n",
month, paymentMade, currentBalance);
}
}
}
Arithmetic expressions- Rules
•Precedence rules for arithmetic operations : Parenthesis first Multiplication, division and mod next Addition subtraction last
Associativity rules : Left to right for arithmetic operations
Type rules : If both operands are integers result is integer If any of the operands is floating point
result is floating
Assignment statement
X = expression
If LHS and RHS are both same type no
conversion
If LHS is floating and RHS is integer RHS
converted to floating
If LHS is integer and RHS is floating RHS
truncated to integer
The value of an assignment is the value
assigned => X = RHS has a value
Assignment statement
Problem :What will be printed by the following
program fragment ?
int x = 2, y = 5, z = 3, p, q, r;
float a;
p = (x + y*z) * 5 + 3/5 * 5;
r = q = 3.0/5 * 5;
a = (5 - 3) /3;
printf(“p = %d\n q = %d\n a = %f\n”, p, q, a);
Assignment statement
int x = 2, y = 5, z = 3, p, q, r;
p = (x + y*z) * 5 + 3/5 * 5;
Assignment statement
int x = 2, y = 5, z = 3, p, q, r;
p = (x + y*z) * 5 + 3/5 * 5;
85
Assignment statement
r = q = 3.0/5 * 5;
q = 3.0/5 * 5 is an assignment.
The value of an assignment is the value
assigned.
The assignment q = 3.0/5 * 5 has a value 3.0.
Thus r = q = 3.0/5 * 5 will assign 3.0 to both q
and r.
Note = is right associative !!
r = q = 3.0/5 * 5;
Conditions
• Relational operators : >, <, >=, <=, !=, ==.
• Logical operators : &&, ||, !
• Exercises:
• If count is 0 and limit is 10, what is the value
of
• (count == 0) && (limit < 20)
• count == 0 && limit < 20
• ! (count == 12)
• (limit < 0) && ((limit/count) > 7) Note why
this does not create a problem.