Loops in Java

In programming languages, loops are used to execute a set of instructions/functions repeatedly when some conditions become true. There are three types of loops in Java.

For loop

While loop

do-while loop

Java Simple For Loop

A simple for loop is the same as C/C++. We can initialize the variable, check condition and increment/decrement value. It consists of four parts:

1. Initialization: It is the initial condition which is executed once when the loop starts. Here, we can initialize the variable, or we can use an already initialized variable. It is an optional condition.

2. Condition: It is the second condition which is executed each time to test the condition of the loop. It continues execution until the condition is false. It must return boolean value either true or false. It is an optional condition.

3. Statement: The statement of the loop is executed each time until the second condition is false.

4. Increment/Decrement: It increments or decrements the variable value. It is an optional condition.

Syntax:

for(initialization;condition;incr/decr){

//statement or code to be executed

}

Example

//program to prints table of 1

public class ForExample {

public static void main(String[] args) {

//Code of Java for loop

for(int i=1;i<=10;i++){

System.out.println(i);

}

}

}

Java While Loop

The Java while loop is used to iterate a part of the program several times. If the number of iteration is not fixed, it is recommended to use while loop.

Syntax:

while(condition){

//code to be executed

}

Example

public class WhileExample {

public static void main(String[] args) {

int i=1;

while(i<=10){

System.out.println(i);

i++;

}

}

}

Java do-while Loop

The Java do-while loop is used to iterate a part of the program several times. If the number of iteration is not fixed and you must have to execute the loop at least once, it is recommended to use do-while loop.

The Java do-while loop is executed at least once because condition is checked after loop body.

Syntax:

do{

//code to be executed

}while(condition);

Example:

public class DoWhileExample {

public static void main(String[] args) {

int i=1;

do{

System.out.println(i);

i++;

}while(i<=10);

}

}