Where can we use while loop?

A common practice when writing software is the need to do the same task some number of times. 

Java while loop is a control flow statement that allows code to be executed repeatedly based on a given Boolean condition. The while loop can be thought of as a repeating if statement.

The while statement

Like all repetition control structures, it has a termination condition, implemented as a boolean expression, that will continue as long as the expression evaluates to true.

Syntax

The syntax of a while loop is

while(condition) {
// body of loop
}

Java while loop example

Here is a simple java while loop example to print numbers from 1 to 7.

package com.yuriyni.java.controlstatements;

public class WhileDemo {
    public static void main(String[] args) {
        int count = 1;

        while (count <= 7) {
            System.out.println("Day of the week: " + count);
            count++;
        }
    }
}

 Output:

Day of the week: 1
Day of the week: 2
Day of the week: 3
Day of the week: 4
Day of the week: 5
Day of the week: 6
Day of the week: 7

The do/while statement

The do-while loop is similar to while loop. Unlike a while loop, though, a do/while loop guarantees that the statement or block will be executed at least once. 

Whereas a while loop is executed zero or more times, a do/while loop is executed one or more times.

Syntax

The syntax of a while loop is

do {
    // loop body
}
while (condition);

Java do-while loop example

package com.yuriyni.java.controlstatements;

public class DoWhileDemo {
    public static void main(String[] args) {
        int count = 8;

        do {
            //However, the body of do...while loop is executed once before the test 
            //expression is checked.
            System.out.println("not checked:" + count);
            count++;
        }while (count <= 7);
    }
}

 Output:

not checked:8