Java Loop Control Statements: Comprehensive Guide

Loop in Java

Java’s iteration statements are for, while, and do-while. These statements create what we commonly call loops.

A loop can be used to tell a program to execute statements repeatedly. Or we can say that, a loop repeatedly executes the same set of instructions until a termination condition is met.

Why Loop is Important ?

Suppose that you need to display a string (e.g., Welcome to Ansari Academy! ) a hundred times. It would be tedious to have to write the following statement a hundred times:

System.out.println("Welcome to Ansari Academy!");
System.out.println("Welcome to Ansari Academy!");
...
...
...
System.out.println("Welcome to Ansari Academy!");

So, how do you solve this problem?

Java hava a powerful feature called a loop that controls how many times an operation or a sequence of operations is performed in succession. Using a loop control statement, you simply tell the computer to display a string a hundred times without having to code the print statement a hundred times, as follows:

// Demonstrate the while loop.
class A {
public static void main(String args[]) {
   int count = 0;
   while (count < 100) {
   System.out.println("Welcome to Ansari Academy!");
   count++;
   }
 }
}

Output

Welcome to Ansari Academy!
Welcome to Ansari Academy!
....
....
....
Welcome to Ansari Academy!
Welcome to Ansari Academy!
Press any key to continue . . .

Explanation

The variable count is initially 0 . The loop checks whether count < 100 is true . If so, it executes the loop body to display the message Welcome to Ansari Academy! and increments count by 1 . It repeatedly executes the loop body until count < 100 becomes false . When count < 100 is false (i.e., when count reaches 100 ), the loop terminates and the next statement after the loop statement is executed

Another important Example ?

// Demonstrate the while loop.
class A {
public static void main(String args[]) {
  int n = 10;
  while(n > 0) {
  System.out.println(n);
  n--;
  }
 }
}

Output

10
9
8
7
6
5
4
3
2
1
Press any key to continue . . .

Types of Loop

Java provides mainly three types of loop statements: while loops, do - while loops, and for loops.