This document discusses different types of loops in Java programming. It introduces while, do-while and for loops. While loops execute statements repeatedly based on a loop condition. Do-while loops are similar but check the condition after executing the loop body once. For loops concisely initialize and update a loop counter variable. The document provides examples of each loop type and how to control loops, including with sentinel values.

1. SWE-103T Object Oriented
Programming
Instructors:
Engr. Anila Saghir
Software Engineering Department
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2. Week 04
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3. Chapter #5
Loops
Chapter 5 introduces the concept of loops,, the loop design strategy to develop
loops, To control a loop with a sentinel value, a while loop, for loops, do while loop,
the similarities and differences between three types of loop statements, nested
loops, program control with break and continue
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4. Introduction
• Loops are constructs that control repeated executions of a block of
statements. Looping in programming languages is a feature which
facilitates the execution of a set of instructions/functions
repeatedly while some condition evaluates to true.
• Java provides three types of loop statements: while loops, do-while
loops, and for loops.
• While all the ways provide similar basic functionality, they differ in
their syntax and condition checking time.
A loop can be used to tell a program to execute statements
repeatedly
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5. The while Loop
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• A while loop executes statements repeatedly while the condition is
true.
• The syntax for the while loop is:
while (loop-continuation-condition) {
// Loop body
Statement(s);
}
5

6. Example
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7. Loop Design Strategies
• Writing a correct loop is not an easy task for novice programmers. Consider three steps when
writing a loop.
• Step 1: Identify the statements that need to be repeated.
• Step 2: Wrap these statements in a loop like this:
while (true) {
Statements;
}
• Step 3: Code the loop-continuation-condition & add appropriate statements to control the loop.
while (loop-continuation-condition) {
Statements;
Additional statements for controlling the loop;
}
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8. • Example: Ask the user to generate table of 2.
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9. Controlling a Loop with a Sentinel Value
• Another common technique for controlling a loop is to designate a
special value when reading and processing a set of values
• This special input value, known as a sentinel value, signifies the
end of the input.
• A loop that uses a sentinel value to control its execution is called a
sentinel-controlled loop
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10. • Example: Ask the user to enter input until he/she enters 0.
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11. Do while loop
• A do-while loop is the same as a while loop except that it executes
the loop body first and then checks the loop continuation
condition.
• The do-while loop is a variation of the while loop. Its syntax is:
do {
// Loop body;
Statement(s);
} while (loop-continuation-condition);
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12. • Example:
import java.util.Scanner;
public class DoWhileProgram {
public static void main(String[] args) {
Scanner input= new Scanner(System.in);
System.out.println("Enter five inputs: ");
int count=1;
do{
System.out.println("Enter "+ count+ (" input: "));
int rollNo=input.nextInt();
System.out.println("The "+ count +" input value is: "+ rollNo );
count++;
}while(count<=5);
}
}
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13. Difference between while and do-while
loops
• The difference between a while loop and a do-while loop is the
order in which the loop-continuation-condition is evaluated and
the loop body executed.
• We can write a loop using either the while loop or the do-while
loop
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14. For Loop
• A for loop has a concise syntax for writing loops. Often we write a
while loop in the following common form:
i = initialValue; // Initialize loop control variable
while (i < endValue){
// Loop body
i++; /
• A for loop can be used to simplify the preceding loop as:
for (i = initialValue; i < endValue; i++){
// Loop body
}
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15. For Loop Syntax
for (initial-action; loop-cont-cond; action-after-each-iteration)
{
// Loop body;
Statement(s);
}
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16. Example 1:
• Ask the user to take 5 inputs.
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17. Example 2 Generate n multiples of 2.
import java.util.Scanner;
public class ForloopProgram {
public static void main(String[] args) {
Scanner input= new Scanner(System.in);
System.out.println("Enter value of n: ");
int multiples, n=input.nextInt();
System.out.println("The multiples of 2 are: ");
for(int i=1; i<=n;i++ ){
multiples=2*i;
System.out.print( multiples+" " );
}
}
}
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18. Tasks
• Calculate the factorial of the number.
• Calculate sum of the numbers from 1 to n
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