for Loop in Java with Example

Last Updated: 28 May, 2022

In Java or any other programming languages, loops play an important role in executing a set of instructions multiple times based on the given condition. Inside a loop block, the set of instructions is fixed and it executes repeatedly while some condition evaluates to true.

For Example, Suppose We have to print the same message 100 times, then rather than typing the same code 100 times, we can use a loop here.

Java provides three basic types of loops:

1. for loop
2. while loop
3. do...while loop

In this tutorial we are going to discuss for loop with definition, diagram and example.

Java for Loop

Java for loop is used to run a set of instructions for a certain number of times as long as given condition is true. A for Loop is consist of three parts Initial Expression, Test Expression (Boolean condition) and Update Expression.

Java for loop Syntax:

for (initialExpression; testExpression; updateExpression) { // body of the loop }

Java for Loop execution flow:

1. Initial Expression: The initialExpression initializes and/or declares variables and executes only once.
2. Test Expression: The condition is evaluated. If the condition is true, the body of the for loop is executed.
3. Body of the Loop: After test expression evaluated true, the body of loop will be executed. The process continues until the condition is false.
4. Update Expression: The updateExpression updates the value of initialExpression. This expression either increase or decrease the variable.
5. Loop Termination: Once test expression becomes false, floop will be terminated automatically.

Flowchart of Java for Loop

Example 1 : Java for Loop Program

// Java Program to demonstrate the example of for loop class ForLoopExample { public static void main(String[] args) { // Printing single message 5 times using for loop for (int i = 1; i <= 5; i++) { System.out.println("javabytechie.com"); } } }

Output

javabytechie.com
javabytechie.com
javabytechie.com
javabytechie.com
javabytechie.com

Java Nested for Loop:

Java also allows to write one for loop inside another for loop, it is knowns as Nested for loop or Inner for loop in Java.

Syntax of Nested for loop in Java

// Outer for loop for (initialExpression; testExpression; updateExpression) { // Inner for loop for (initialExpression; testExpression; updateExpression) { // Code } }

Now, let's understand Nested for loop through the given example.

Example 2 : Java Nested for Loop

public class NestedForLoopExample { public static void main(String[] args) { // Outer for loop for (int i = 1; i <= 3; i++) { System.out.println("Outer for loop"); // Inner for loop for (int j = 1; j <= 4; j++) { System.out.println("Inner for loop"); } } } }

Output

Outer for loop
Inner for loop
Inner for loop
Inner for loop
Inner for loop
Outer for loop
Inner for loop
Inner for loop
Inner for loop
Inner for loop
Outer for loop
Inner for loop
Inner for loop
Inner for loop
Inner for loop

Multiple for Loop Variables

We can also use more than one variable in the for loop initialization, test expression, and for the step value. In this type of for loop, we can have only one boolean test expression.

Example 3 : Multiple for Loop Variables

public class MultipleForLoopVariablesExample { public static void main(String[] args) { for (int i = 1, j = 1, k = 1; (i + j + k) <= 20; i++, j++, k++) { System.out.println("Sum of (i + j + k) = " + (i + j + k)); } } }

Output

Sum of (i + j + k) = 3
Sum of (i + j + k) = 6
Sum of (i + j + k) = 9
Sum of (i + j + k) = 12
Sum of (i + j + k) = 15
Sum of (i + j + k) = 18

Infinite for Loop in Java

A loop that does not terminate that loop is known as an Infinite loop in Java.

Example 4 : Infinite for Loop in Java

public class InfiniteForLoopExample { public static void main(String args[]) { for( ; ; ) { System.out.println("It's an Infinite Loop"); } } }

Output

It's an Infinite Loop
It's an Infinite Loop
It's an Infinite Loop
It's an Infinite Loop
It's an Infinite Loop
It's an Infinite Loop
It's an Infinite Loop
It's an Infinite Loop
...
...
...

Continue and Break Statements inside for Loop

We can use continue and break statements inside for loop according to our requirement.

In Java, the continue statement is mainly used inside the loops such as for loop, while loop, do-while loop, etc. The purpose of the continue statement is to continue the current running flow of the Java program and skip the rest of the code at the specified condition.

A break statement is used to terminate the current processing of the loop, after the termination control returns from the loop immediately to the next statement after the loop.

Let's understand the below Java program where we are iterating a loop from 1 to 30 but printing the even value from 11-20.

Example 5 : Continue and Break Statements inside for Loop

public class ContinueAndBreakInForLoop { public static void main(String[] args) { for(int i = 1; i <= 30; i++) { // Continue statement if(i < 11) continue; // Printing even number if(i % 2 == 0) System.out.println("Even Number: " + i); // Break Statement if(i > 20) break; } } }

Output

Even Number: 12
Even Number: 14
Even Number: 16
Even Number: 18
Even Number: 20