Java Program to Swap Two Numbers

In this quick article, we will learn two techniques to swap two numbers in Java. The first one uses a temporary variable for swapping, while the second one doesn't use any temporary variables.

1. Java program to swap two numbers using a temporary variable

package com.javaguides.java.tutorial;

import java.util.Scanner;

/**
 * Java Program to Swap Two Numbers
 * 
 * @author https://www.javaguides.net/
 *
 */
public class JavaProgram {
    public static void main(String[] args) {

        try (Scanner scanner = new Scanner(System.in)) {

            System.out.print("Enter first number:");
            int first = scanner.nextInt();
            System.out.print("Enter second number:");
            int second = scanner.nextInt();

            System.out.println("--Before swap--");
            System.out.println("First number = " + first);
            System.out.println("Second number = " + second);

            // Value of first is assigned to temporary
            int temporary = first;

            // Value of second is assigned to first
            first = second;

            // Value of temporary (which contains the initial value of first) is assigned to
            // second
            second = temporary;

            System.out.println("--After swap--");
            System.out.println("First number = " + first);
            System.out.println("Second number = " + second);
        }
    }
}

Output:

Enter first number:10
Enter second number:20
--Before swap--
First number = 10
Second number = 20
--After swap--
First number = 20
Second number = 10

2. Java program to swap two numbers without using a temporary variable

Let's rewrite the above Java program to swap two numbers without using a temporary variable:

package com.javaguides.java.tutorial;

import java.util.Scanner;

/**
 * Java Program to Swap Two Numbers
 * 
 * @author https://www.sourcecodeexamples.net/
 *
 */
public class JavaProgram {
    public static void main(String[] args) {

        try (Scanner scanner = new Scanner(System.in)) {

            System.out.print("Enter first number:");
            int first = scanner.nextInt();
            System.out.print("Enter second number:");
            int second = scanner.nextInt();

            System.out.println("--Before swap--");
            System.out.println("First number = " + first);
            System.out.println("Second number = " + second);

            first = first - second;
            second = first + second;
            first = second - first;

            System.out.println("--After swap--");
            System.out.println("First number = " + first);
            System.out.println("Second number = " + second);
        }
    }
}

Output:

Enter first number:10
Enter second number:20
--Before swap--
First number = 10
Second number = 20
--After swap--
First number = 20
Second number = 10

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