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swap-two-numbers.mdx

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title Java Program to Swap Two Numbers
shortTitle Swap Two Numbers
description Learn different ways to swap two numbers in Java — using a temporary variable, arithmetic operations, and bitwise XOR — with clear examples and outputs.

Swapping two numbers is a common beginner-friendly exercise in Java. Below are three simple ways to do it:

  • Using a temporary variable (safest and most readable)
  • Using arithmetic operations (beware of overflow for very large numbers)
  • Using bitwise XOR (no temp variable; works for integers)

Before you start, you may want to review:

1) Swap Using a Temporary Variable

This is the most straightforward and recommended approach.

Example

class Main {
  public static void main(String[] args) {
    int a = 10;
    int b = 20;

    System.out.println("Before swap: a = " + a + ", b = " + b);

    int temp = a; // store a
    a = b;        // put b into a
    b = temp;     // put original a into b

    System.out.println("After swap:  a = " + a + ", b = " + b);
  }
}

Output

Before swap: a = 10, b = 20
After swap:  a = 20, b = 10

2) Swap Without Temp (Arithmetic)

Uses addition and subtraction. Note: This can overflow if the numbers are near the integer limits.

Example

class Main {
  public static void main(String[] args) {
    int a = 15;
    int b = 27;

    System.out.println("Before swap: a = " + a + ", b = " + b);

    a = a + b; // a becomes sum
    b = a - b; // b becomes original a
    a = a - b; // a becomes original b

    System.out.println("After swap:  a = " + a + ", b = " + b);
  }
}

Output

Before swap: a = 15, b = 27
After swap:  a = 27, b = 15

3) Swap Using XOR (No Temp)

Works for integers and avoids extra memory, but is less readable for beginners.

Example

class Main {
  public static void main(String[] args) {
    int a = 5;
    int b = 9;

    System.out.println("Before swap: a = " + a + ", b = " + b);

    a = a ^ b; // Step 1
    b = a ^ b; // Step 2: now b is original a
    a = a ^ b; // Step 3: now a is original b

    System.out.println("After swap:  a = " + a + ", b = " + b);
  }
}

Output

Before swap: a = 5, b = 9
After swap:  a = 9, b = 5

Which Method Should You Use?

  • Prefer the temporary variable method for clarity and safety.
  • The arithmetic method can be a neat trick, but avoid it when values may overflow.
  • XOR is an interesting technique; use it only when it adds real value and readability is not sacrificed.