In this Java program, we will learn how to swap two numbers. Swapping means exchanging the values of two variables.
For example, if:
a = 10
b = 20After swapping:
a = 20
b = 101. Normal Java Program Using a Temporary Variable
import java.util.Scanner;
public class SwapTwoNumbers {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter first number: ");
int a = sc.nextInt();
System.out.print("Enter second number: ");
int b = sc.nextInt();
System.out.println("Before Swapping:");
System.out.println("a = " + a);
System.out.println("b = " + b);
int temp = a;
a = b;
b = temp;
System.out.println("After Swapping:");
System.out.println("a = " + a);
System.out.println("b = " + b);
sc.close();
}
}Output
Enter first number: 10
Enter second number: 20
Before Swapping:
a = 10
b = 20
After Swapping:
a = 20
b = 10Explanation
A temporary variable is used to store the value of the first number:
int temp = a;Then the value of b is assigned to a:
a = b;Finally, the value stored in temp is assigned to b:
b = temp;This exchanges the values of a and b.
Swapping Process
temp = a
a = b
b = temp2. Java 8 Program to Swap Two Numbers
Java 8 does not provide a special swapping feature for primitive variables. The simplest approach is still to use a temporary variable.
We can, however, demonstrate the operation using a Java 8 lambda expression:
import java.util.Scanner;
import java.util.function.BiFunction;
public class SwapTwoNumbersJava8 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter first number: ");
int a = sc.nextInt();
System.out.print("Enter second number: ");
int b = sc.nextInt();
System.out.println("Before Swapping:");
System.out.println("a = " + a);
System.out.println("b = " + b);
BiFunction<Integer, Integer, int[]> swap =
(x, y) -> new int[]{y, x};
int[] result = swap.apply(a, b);
a = result[0];
b = result[1];
System.out.println("After Swapping:");
System.out.println("a = " + a);
System.out.println("b = " + b);
sc.close();
}
}Output
Enter first number: 10
Enter second number: 20
Before Swapping:
a = 10
b = 20
After Swapping:
a = 20
b = 10Explanation of Java 8 Program
The Java 8 version uses the BiFunction functional interface:
BiFunction<Integer, Integer, int[]>The lambda expression receives two numbers and returns them in reverse order:
(x, y) -> new int[]{y, x}The apply() method executes the lambda expression:
int[] result = swap.apply(a, b);The returned values are then assigned back to a and b.
Difference Between Normal Java and Java 8
| Feature | Normal Java | Java 8 |
|---|---|---|
| Approach | Temporary variable | Lambda + BiFunction |
| Easy to understand | Yes | Moderate |
| Extra object | No | int[] |
| Java 8 feature | No | Lambda expression |
| Recommended | Yes | For learning Java 8 |
Conclusion
The temporary variable approach is the simplest and most recommended way to swap two numbers in Java. The Java 8 version demonstrates how a lambda expression and BiFunction can be used to perform the same operation.
For beginners, understanding the traditional approach first is important before moving to Java 8 functional programming.
