Java Program to Swap Two Numbers

Last Updated : 11 Oct, 2025

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Problem Statement: Given two integers m and n. The goal is simply to swap their values in the memory block and write the java code demonstrating approaches.

Illustration:

Input : m=9, n=5
Output : m=5, n=9
Input : m=15, n=5
Output : m=5, n=15
Here 'm' and 'n' are integer value

Swap Two Numbers

Approach 1: Using a Temporary Variable

A temporary memory cell is created to hold one value during the swap.
The value in the temporary variable is assigned to the other variable after swapping.
The temporary variable acts as a helper and does not appear in the final output.

Java

public class GFG{
    public static void main(String[] args){
        
        int m = 9, n = 5;
        System.out.println("Before swapping: m = " + m + ", n = " + n);

        int temp = m;
        m = n;
        n = temp;

        System.out.println("After swapping: m = " + m + ", n = " + n);
    }
}

Output

Before swapping: m = 9, n = 5
After swapping: m = 5, n = 9

Note: This swap only affects local copies in memory. If you pass m and n to a method, the original variables remain unchanged due to Java's pass-by-value.

Approach 2: Using Arithmetic (Sum and Difference)

Algorithms: There are 3 standard steps as listed below:

Subtract the second number from the first and store the result in the first variable.
Add both numbers and store the result in the second variable.
Subtract the new first variable from the second to get the original first number in the first variable.

Java

public class GFG{
    public static void main(String[] args){
        
        int m = 9, n = 5;
        System.out.println("Before swapping: m = " + m + ", n = " + n);

        m = m + n;  
        n = m - n;  
        m = m - n; 

        System.out.println("After swapping: m = " + m + ", n = " + n);
    }
}

Output

Before swapping: m = 9, n = 5
After swapping: m = 5, n = 9

Note: This method avoids extra variables but can cause overflow with very large numbers.

Approach 3: Using Bitwise XOR Operator

Operates on individual bits of integer types (char, short, int, etc.).
Returns 1 for each bit position where the corresponding bits of the two operands are different; otherwise returns 0.
Commonly used in swapping numbers without a temporary variable and in bit manipulation tasks.

Illustration:

a = 5 -> 0101 (binary)
b = 7 -> 0111 (binary)
XOR Operation: a ^ b
0101
^ 0111
------
0010 -> 2 (decimal)

Using XOR twice can swap two numbers efficiently without extra memory:

a = a ^ b;
b = a ^ b;
a = a ^ b;

Java

public class GFG {
    public static void main(String[] args){
        
        int m = 9, n = 5;
        System.out.println("Before swapping: m = " + m
                           + ", n = " + n);

        // Step 1: XOR m and n, store result in m
        m = m ^ n;
        
        // Step 2: XOR new m with n to get original m in n
        n = m ^ n;
        
        // Step 3: XOR new m with new n to
        // get original n in m
        m = m ^ n;

        System.out.println("After swapping: m = " + m
                           + ", n = " + n);
    }
}

Output

Before swapping: m = 9, n = 5
After swapping: m = 5, n = 9

How do we swap using a function and reflect the changes outside?

The previous methods only swaps local copies. To swap numbers in a method and reflect changes outside, we use an array.

Java

public class SwapUsingArray {

    public static void main(String[] args){
        
        // Initialize numbers in an array
        int[] nums = { 9, 5 };

        System.out.println("Before swapping: m = " + nums[0]
                           + ", n = " + nums[1]);

        // Call the method to swap the numbers
        swapArray(nums);

        // Print the numbers after swapping
        System.out.println(
            "After swapping using array: m = " + nums[0]
            + ", n = " + nums[1]);
    }

    // Method to swap numbers in an array
    public static void swapArray(int[] arr){
        
        // Temporary variable to hold the first value
        int temp = arr[0];
        
        // Assign second value to first
        arr[0] = arr[1];
        
        // Assign temporary value to second
        arr[1] = temp; 
    }
}

Output

Before swapping: m = 9, n = 5
After swapping using array: m = 5, n = 9

Swap Two Numbers

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