Java Program to Reverse a Given String

This page contains a Java program that reverses a given string. The program uses basic string manipulation techniques to achieve this task.

Program Explanation

The Java program to reverse a string follows these steps:

1. Define the main class: Create a public class named ReverseString.
2. Main Method: The main method is the entry point of the program.
3. Input String: Define a string that you want to reverse.
4. Reverse the String: Use a loop to reverse the string by iterating from the end to the beginning.
5. Print the Result: Output the reversed string to the console.

Java Program Code

/**
 * Java program to reverse a given string.
 */
public class ReverseString {

    /**
     * Main method which is the entry point of the program.
     * @param args command-line arguments
     */
    public static void main(String[] args) {
        // Define the string to be reversed
        String original = "Hello, World!";
        
        // Call the reverse method and store the result
        String reversed = reverseString(original);
        
        // Print the reversed string
        System.out.println("Original String: " + original);
        System.out.println("Reversed String: " + reversed);
    }
    
    /**
     * Method to reverse a given string.
     * @param str the string to be reversed
     * @return the reversed string
     */
    public static String reverseString(String str) {
        // Create a StringBuilder object with the original string
        StringBuilder sb = new StringBuilder(str);
        
        // Reverse the string using the StringBuilder reverse method
        return sb.reverse().toString();
    }
}

Program Details

The ReverseString class contains the following:

• main Method: The entry point of the program where the string is defined and the reverse method is called.
• reverseString Method: A static method that takes a string as input, reverses it using the StringBuilder class, and returns the reversed string.

Running the Program

To run the program:

1. Save the code in a file named ReverseString.java.
2. Compile the program using the command: javac ReverseString.java.
3. Run the compiled program using the command: java ReverseString.

Explanation of the Java Program:

1. Class Definition: The class ReverseString contains all the methods and logic needed to reverse the string.
2. Main Method:
   • Initializes a string original with a value to be reversed.
   • Calls the reverseString method and stores the result in reversed.
   • Prints both the original and reversed strings to the console.
3. reverseString Method:
   • Uses StringBuilder, a mutable sequence of characters, which allows efficient manipulation of the string.
   • The reverse() method of StringBuilder reverses the characters.
   • Returns the reversed string as a new string.