Loop is a programming construct that allows you to execute a block of code repeatedly based on a condition. Loops in Java can be categorized based on when the loop condition is checked relative to the execution of the loop body.
These categories are commonly referred to as entry-controlled loops and exit-controlled loops.
These categories are entry-controlled and exit-controlled loops
Entry-Controlled Loop (Pre-Test Loop):
In entry-controlled loops, the loop condition is checked before the execution of the loop body. If the condition evaluates to false initially, the loop body will not be executed at all. Example of Entry-Controlled Loops:
while loop:
The java program while loop is used when you want to execute a block of code as long as a condition is true. Given condition is tested before executing the loop body.
Syntax:
while (condition) {
// code to be executed
}
condition: It is the expression evaluated before each iteration. If it evaluates to true, the loop continues; otherwise, it terminates.
// Entry-controlled while loop
int i = 0;
while (i < 5) {
System.out.println(“Count is: “ + i);
i++;
}
for loop:
The java for loop is used when you know exactly how many times you want to execute a block of code.
Syntax:
for (initialization; condition; update) {
// code to be executed
}
Initialization: It initializes the loop control variable.
Condition: Expression evaluated before each iteration. If it evaluates to true then the loop continues otherwise it terminates.
Update: It updates the loop control variable after each iteration.
// Entry-controlled for loop
for (int i = 0; i < 5; i++) {
System.out.println(“Count is: “ + i);
}
Exit-Controlled Loop (Post-Test Loop):
In exit-controlled loops, the loop condition is checked after the execution of the loop body. This means that the loop body is executed at least once before the condition is evaluated.
do-while loop
The do-while loop is similar to the while loop, but the condition is evaluated after executing the loop body. Therefore, the loop body is executed at least once.
Syntax:
do {
// code to be executed
} while (condition);
// Exit-controlled do-while loop
int i = 0;
do {
System.out.println(“Count is: “ + i);
i++;
} while (i < 5);
Use Case 1:
Generating table of N.
Input: N=9
Output:
9 X 1Â : 9
9 X 2Â : 18
9 X 3Â : 27
9 X 4Â : 36
9 X 5Â : 45
9 X 6Â : 54
9 X 7Â : 63
9 X 8Â : 72
9 X 9Â : 81
9 X 10Â : 90
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