Swap Without Variable Example in Java

Introduction

Swap Without Variable is a classic Java console program that demonstrates the concept with complete source code and sample output. Calculation programs apply formulas to solve geometry, statistics and numeric problems.

This tutorial walks through the program line by line, explains how the logic works, and highlights best practices you can apply in your own code.

Definition

The act of swapping two variables refers to mutually exchanging the values of the variables. Usually, this is done with the data in memory.

Swap Without Variable Example Program

import java.util.Scanner;
 
class SwapWithoutVariable{
	public static void main(String args[]){
		int num1,num2;
		System.out.println("Enter num1 and num2");
		Scanner in = new Scanner(System.in);
		num1 = in.nextInt();
		num2 = in.nextInt();
		System.out.println("Before Swapping num1 = "+num1+" and num2 = "+num2);
		num1 = num1 + num2;
		num2 = num1 - num2;
		num1 = num1 - num2;
		System.out.println("After Swapping num1 = "+num1+" and num2 = "+num2);
	}
}

Sample Output

Enter num1 and num2
67
78
Before Swapping num1 = 67 and num2 = 78
After Swapping num1 = 78 and num2 = 67

When to use

Use these formulas in homework tools, engineering calculators or anywhere repeated numeric computation is needed.

How it works

1. Execution begins in the main method — the JVM calls this method when you run the class.

2. import java.util.Scanner; imports a class used later in the program.

3. A println / print call writes text to the console — part of the sample output below.

4. A Scanner reads typed input from the keyboard (System.in).

5. num1 = in.nextInt(); updates a variable used in the calculation or output.

6. num2 = in.nextInt(); updates a variable used in the calculation or output.

7. A println / print call writes text to the console — part of the sample output below.

8. A println / print call writes text to the console — part of the sample output below.

Best Practices

• Use meaningful variable and class names that describe their purpose.
• Compile and run the program locally — modify values to see how output changes.
• Read compiler errors carefully; they usually point to the exact line to fix.

Common Mistakes

• Copying code without understanding each line — practice by changing one statement at a time.
• Mismatching the public class name and the .java filename.
• Forgetting semicolons at the end of statements.