Java for Keyword

The for keyword in Java is used to create a loop that repeatedly executes a block of code a specific number of times. It is commonly used for iterating over arrays and collections.

Table of Contents

1. Introduction
2. for Keyword Syntax
3. Understanding for
4. Examples
   • Basic Usage
   • Using for with Arrays
   • Using Enhanced for Loop
5. Real-World Use Case
6. Conclusion

Introduction

The for loop in Java is a control flow statement that allows code to be executed repeatedly based on a given boolean condition. It is particularly useful when the number of iterations is known beforehand.

for Keyword Syntax

The syntax for the for loop is as follows:

for (initialization; condition; update) {
    // code to be executed
}

Example:

for (int i = 0; i < 10; i++) {
    System.out.println(i);
}

Understanding for

The for loop consists of three parts:

• Initialization: This part is executed only once, at the beginning. It is typically used to initialize a loop control variable.
• Condition: This part is evaluated before each iteration. If the condition is true, the loop body is executed. If it is false, the loop terminates.
• Update: This part is executed after each iteration of the loop. It is typically used to update the loop control variable.

Key Points:

• All three parts are optional, but the semicolons ; are mandatory.
• The loop body can be a single statement or a block of statements enclosed in curly braces {}.

Examples

Basic Usage

To demonstrate the basic usage of the for keyword, we will print numbers from 0 to 9.

Example

public class ForExample {
    public static void main(String[] args) {
        for (int i = 0; i < 10; i++) {
            System.out.println(i);
        }
    }
}

Output:

0
1
2
3
4
5
6
7
8
9

Using for with Arrays

The for loop is often used to iterate over elements in an array.

Example

public class ForArrayExample {
    public static void main(String[] args) {
        int[] numbers = {10, 20, 30, 40, 50};

        for (int i = 0; i < numbers.length; i++) {
            System.out.println("Element at index " + i + ": " + numbers[i]);
        }
    }
}

Output:

Element at index 0: 10
Element at index 1: 20
Element at index 2: 30
Element at index 3: 40
Element at index 4: 50

Using Enhanced for Loop

The enhanced for loop, also known as the "for-each" loop, simplifies iteration over arrays and collections.

Example

public class EnhancedForExample {
    public static void main(String[] args) {
        int[] numbers = {10, 20, 30, 40, 50};

        for (int number : numbers) {
            System.out.println("Number: " + number);
        }
    }
}

Output:

Number: 10
Number: 20
Number: 30
Number: 40
Number: 50

Real-World Use Case

Iterating Over a List of Items

In real-world applications, the for loop is useful for iterating over lists of items, such as processing user inputs, handling collections, or performing repetitive tasks.

Example

import java.util.ArrayList;
import java.util.List;

public class ForListExample {
    public static void main(String[] args) {
        List<String> fruits = new ArrayList<>();
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Cherry");

        for (String fruit : fruits) {
            System.out.println("Fruit: " + fruit);
        }
    }
}

Output:

Fruit: Apple
Fruit: Banana
Fruit: Cherry

Conclusion

The for keyword in Java is used for creating loops that can execute a block of code multiple times. It is especially useful for iterating over arrays and collections. By understanding and using the for loop, you can efficiently manage repetitive tasks and handle collections of data in your Java programs.