Java Swap of two data with out third variable Code

To swap two variables in Java without using a third variable, you can use arithmetic operations or bitwise XOR, and it has mathematical history rooted in algebra and logic gates. Here’s how you can do it:

Behind the Scenes: Why It's Interesting

Swapping variables is fundamental in:

Sorting algorithms (e.g., Bubble Sort, Selection Sort)
Register-level computing (assembly)
Interview puzzles

Doing it without a temporary variable shows an understanding of memory, logic, and math.

Using Arithmetic Operations

java

public class SwapWithoutThirdVariable {

public static void main(String[] args) {

int a = 30;

int b = 40;

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

// Interchange values using arithmetic operations

a = a + b; // The variable value a now reflects the total result of a and b

b = a - b; //The variable value b now catch the original value of a

a = a - b; // The variable value a now reflects the original value of b

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

}

Using Bitwise XOR

java

public class SwapWithoutThirdVariable {

public static void main(String[] args) {

int a = 30;

int b = 40;

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

// Interchange values using bitwise XOR

a = a ^ b; // The variable a now reflects the result of a XOR b

b = a ^ b; // b currently catch the initial value of a

a = a ^ b; // a currently catch the initial value of b

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

}

Explanation

Arithmetic Operations:

a = a + b: Adds the values of a and b and stores the result in a.
b = a - b: Subtracts b from the new value of a (which is a + b), giving the original value of a.
a = a - b: Subtracts the new value of b (which is the original value of a) from a (which is a + b), giving the original value of b.

Bitwise XOR:

a = a ^ b: Computes the XOR of a and b and stores it in a.
b = a ^ b: XORs the new value of a (which is a ^ b) with b, yielding the original value of a.
a = a ^ b: XORs the new value of a (which is a ^ b) with the new value of b (which is the original value of a), yielding the original value of b.

Ex-plain:

A B A^B (A XOR B)

0 0 0 (zero because operands are same)

0 1 1

1 0 1 (one because operands are different)

1 1 0

Historical & Mathematical Roots

🔷 1. Algebraic Swap (Addition-Subtraction)

From basic algebra: rearranging equations
Invented for low-level memory optimization, especially on machines with limited registers
Risk: Might cause overflow if a + b exceeds the int range

🔷 2. Bitwise XOR Swap

Comes from Boolean algebra and logic gates:

XOR is reversible
Originates from digital circuit theory
XOR logic is used in CPU registers and low-level firmware

Comparison Table

Method	Safe from Overflow	Bitwise Knowledge	Memory Used	Speed	History Root
Add/Subtract	❌ No	✅ Basic	✅ No temp	⚡ Fast	Algebra (Ancient)
XOR	✅ Yes	✅ Required	✅ No temp	⚡ Fast	Boolean Logic
Temp variable	✅ Yes	❌ Not needed	❌ Needs 1	✅ Fast	High-level Logic

Summary

Both techniques accomplish the exchange without the need for a temporary variable. The XOR method is more elegant and avoids potential issues with integer overflow, but the arithmetic method is often easier to understand.

In short:

Add/Subtract method = algebraic manipulation from basic math
XOR method = inspired by logic gates and binary operations from computer architecture