Java Examples - Using for and foreach Loops

Java Examples

The for statement is straightforward and used for looping through data.

The number of times a for loop executes is determined before execution. The syntax is as follows:

for(initialization; boolean expression; update) {
    // Code statements
}

The foreach statement is one of the new features in Java 5, providing significant convenience for developers when iterating over arrays and collections.

The foreach syntax is as follows:

for(element type t element variable x : iterable object obj) {
     Java statement referencing x;
}

The following example demonstrates the use of for and foreach loops:

Main.java File

public class Main {
    public static void main(String[] args) {
        int[] intary = { 1, 2, 3, 4 };
        forDisplay(intary);
        foreachDisplay(intary);
    }
    public static void forDisplay(int[] a) {  
        System.out.println("Using for loop to iterate over the array");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i] + " ");
        }
        System.out.println();
    }
    public static void foreachDisplay(int[] data) {
        System.out.println("Using foreach loop to iterate over the array");
        for (int a : data) {
            System.out.print(a + " ");
        }
    }
}

The output of the above code is:

Using for loop to iterate over the array
1 2 3 4 
Using foreach loop to iterate over the array
1 2 3 4

Main.java File

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

public class Main {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};

        System.out.println("----------Using for Loop------------");
        for(int i = 0; i < arr.length; i++) {
            System.out.println(arr[i]);
        }

        System.out.println("---------Using For-Each Loop-------------");

        // Enhanced for-each loop
        for(int element : arr) {
            System.out.println(element);
        }

        System.out.println("---------For-Each Loop for 2D Array-------------");

        // Iterating over a 2D array
        int[][] arr2 = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
        for(int[] row : arr2) {
            for(int element : row) {
                System.out.println(element);
            }
        }

        // Traversing a List in three ways
        List<String> list = new ArrayList<String>();

        list.add("Google");
        list.add("tutorialpro");
        list.add("Taobao");

System.out.println("----------Method 1: Regular for loop-----------");
for(int i = 0; i < list.size(); i++)
{
    System.out.println(list.get(i));
}

System.out.println("----------Method 2: Using Iterator-----------");
for(Iterator<String> iter = list.iterator(); iter.hasNext();)
{
    System.out.println(iter.next());
}

System.out.println("----------Method 3: For-Each Loop-----------");
for(String str: list)
{
    System.out.println(str);
}

The above code outputs:

----------Using for loop------------
1
2
3
4
5
---------Using For-Each loop-------------
1
2
3
4
5
---------For-Each loop for 2D array-------------
1
2
3
4
5
6
7
8
9
----------Method 1: Regular for loop-----------
Google
tutorialpro
Taobao
----------Method 2: Using Iterator-----------
Google
tutorialpro
Taobao
----------Method 3: For-Each Loop-----------
Google
tutorialpro
Taobao

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