title: Java for Loop

description: In this tutorial, we will learn how to use for loop in Java with the help of examples and we will also learn about the working of Loop in computer programming.

import NextImage from 'next/image';

In computer programming, loops are used to repeat a block of code. For example, if you want to show a message 100 times, then rather than typing the same code 100 times, you can use a loop.

In Java, there are three types of loops.

- for loop

- while loop

- do...while loop

This tutorial focuses on the for loop. You will learn about the other type of loops in the upcoming tutorials.

Java `for` loop is used to run a block of code for a certain number of times. The syntax of `for` loop is:

for (initialExpression; testExpression; updateExpression) {

// body of the loop

}

Here,

1. The **initialExpression** initializes and/or declares variables and executes only once.

2. The **condition** is evaluated. If the **condition** is `true`, the body of the `for` loop is executed.

3. The **updateExpression** updates the value of **initialExpression**.

4. The **condition** is evaluated again. The process continues until the **condition** is `false`.

To learn more about the conditions, visit [Java relational](operators#3-java-relational-operators) and [logical operators](operators#4-java-logical-operators).

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<NextImage

className="object-cover object-center shadow-xl"

alt="Working of Java if statement"

src={require('@/img/docs/working-of-for-loop.svg').default}

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height={1307}

layout="responsive"

blurDataURL={require('@/img/docs/working-of-for-loop.svg').default}

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loading="lazy"

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<p align="center" className="text-base text-gray-600 font-medium">Flowchart of Java for loop</p>

</div>

class Main {

public static void main(String[] args) {

int n = 5;

// for loop

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

System.out.println("Java is fun");

}

}

}

Here is how this program works.

| Iteration | Variable | Condition: i <= n | Action |

| :-------: | :--------------: | :---------------: | :-------------------------------------------------: |

| 1st | `i = 1`, `n = 5` | `true` | `Java is fun` is printed `i` is increased to **2**. |

| 2nd | `i = 2`, `n = 5` | `true` | `Java is fun` is printed `i` is increased to **3**. |

| 3rd | `i = 3`, `n = 5` | `true` | `Java is fun` is printed `i` is increased to **4**. |

| 4th | `i = 4`, `n = 5` | `true` | `Java is fun` is printed `i` is increased to **5**. |

| 5th | `i = 5`, `n = 5` | `true` | `Java is fun` is printed `i` is increased to **6**. |

| 6th | `i = 6`, `n = 5` | `false` | The loop is terminated. |

class Main {

public static void main(String[] args) {

int n = 5;

// for loop

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

System.out.println(i);

}

}

}

Here is how the program works.

| Iteration | Variable | Condition: i <= n | Action |

| :-------: | :--------------: | :---------------: | :---------------------------------------: |

| 1st | `i = 1`, `n = 5` | `true` | `1` is printed `i` is increased to **2**. |

| 2nd | `i = 2`, `n = 5` | `true` | `2` is printed `i` is increased to **3**. |

| 3rd | `i = 3`, `n = 5` | `true` | `3` is printed `i` is increased to **4**. |

| 4th | `i = 4`, `n = 5` | `true` | `4` is printed `i` is increased to **5**. |

| 5th | `i = 5`, `n = 5` | `true` | `5` is printed `i` is increased to **6**. |

| 6th | `i = 6`, `n = 5` | `false` | The loop is terminated. |

class Main {

public static void main(String[] args) {

int sum = 0;

int n = 1000;

// for loop

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

// body inside for loop

sum += i; // sum = sum + i

}

System.out.println("Sum = " + sum);

}

}

Here, the value of `sum` is **0** initially. Then, the for loop is iterated from `i = 1 to 1000`. In each iteration, `i` is added to `sum`and its value is increased by **1**.

When `i` becomes **1001**, the test condition is `false` and `sum` will be equal to `0 + 1 + 2 + .... + 1000`.

The above program to add the sum of natural numbers can also be written as

class Main {

public static void main(String[] args) {

int sum = 0;

int n = 1000;

// for loop

for (int i = n; i >= 1; --i) {

// body inside for loop

sum += i; // sum = sum + i

}

System.out.println("Sum = " + sum);

}

}

The output of this program is the same as the **Example 3**.

The Java for loop has an alternative syntax that makes it easy to iterate through [arrays](arrays) and collections. For example,

class Main {

public static void main(String[] args) {

// create an array

int[] numbers = {3, 7, 5, -5};

// iterating through the array

for (int number: numbers) {

System.out.println(number);

}

}

}

Here, we have used the **for-each loop** to print each element of the `numbers` array one by one.

In the first iteration of the loop, `number` will be 3, `number` will be 7 in second iteration and so on.

To learn more, visit [Java for-each Loop](enhanced-for-loop).

If we set the test expression in such a way that it never evaluates to false, the for loop will run forever. This is called infinite for loop. For example,

class Infinite {

public static void main(String[] args) {

int sum = 0;

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

System.out.println("Hello");

}

}

}

Here, the test expression ,`i <= 10`, is never `false` and Hello is printed repeatedly until the memory runs out.