Swap Two Numbers in Java

What You’ll Learn

Swapping exchanges two variables so each holds the other’s old value: a=5, b=10 becomes a=10, b=5. You will use a temp variable, an arithmetic no-temp swap, and an optional XOR trick for integers — plus a live preview and worked examples.

📝 Problem & Approach

Given two variables, exchange their values so each holds what the other used to hold.

// Before: a = 5,  b = 10
// After:  a = 10, b = 5

Inputs & Outputs

Minimal workflow

temp = a
a = b
b = temp

Method comparison

🔮 Live Preview

Enter two integers and swap them with a temporary variable.

Press “Swap”.

Examples Gallery

Three complete Java programs — temp variable, arithmetic without temp, and XOR for integers. Click View Output to reveal sample console results.

public class SwapTemp {
    public static void main(String[] args) {
        int num1 = 5;
        int num2 = 10;

        System.out.println("Before swapping: num1 = " + num1 + ", num2 = " + num2);
        int temp = num1;
        num1 = num2;
        num2 = temp;
        System.out.println("After swapping: num1 = " + num1 + ", num2 = " + num2);
    }
}

Before swapping: num1 = 5, num2 = 10
After swapping: num1 = 10, num2 = 5

public class SwapArithmetic {
    public static void main(String[] args) {
        int num1 = 5;
        int num2 = 10;

        System.out.println("Before swapping: num1 = " + num1 + ", num2 = " + num2);
        num1 = num1 + num2;
        num2 = num1 - num2;
        num1 = num1 - num2;
        System.out.println("After swapping: num1 = " + num1 + ", num2 = " + num2);
    }
}

Before swapping: num1 = 5, num2 = 10
After swapping: num1 = 10, num2 = 5

public class SwapXor {
    public static void main(String[] args) {
        int a = 5;
        int b = 10;

        if (a != b) {
            a ^= b;
            b ^= a;
            a ^= b;
        }

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

After swapping: a = 10, b = 5

🔎 Worked Walkthrough — 5 and 10

Follow the temp variable through each assignment.

If you assign a = b first without saving, the original 5 disappears.

⚖️ Facts Worth Knowing

Handy follow-ups interviewers sometimes ask.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

Swapping two variables does a fixed number of assignments regardless of the values.

💡 Best Practices