Java String Class Reverse Program

Task: Write a Java String Class Reverse Program. You have to use only String class objects and String class built-in methods to reverse a user supplied string.

Logic behind Java String Reverse Program

You will use the following standard methods provided in String class:

1. length() method to know the length of the original string.
2. charAt(index) method to get a particular character from a string at given index.
3. You will use + operator for string concatenation.

The actual logic behind this Reverse string Java Program is to take the last character from original string and place it in a second string at start. Next time the second last character will be obtained and concatenated with second string, and so on. So we will use a for loop form s1.length()-1 down to zero.

Java String Class Reverse Program

The Code of Java String Reverse Program

/*How you will reverse a string using String class only.*/

import java.util.Scanner;

/**
 *
 * @author www.EasyCodeBook.com
 */
public class StringReverse {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        
        Scanner input = new Scanner(System.in);
        System.out.print("Enter a String to Reverse: ");
        String s1=input.nextLine();
        String s2="";
        
        for(int i=s1.length()-1;i>=0;i--)
           s2=s2+s1.charAt(i);
        
        System.out.println("Original string=" + s1);                
        System.out.println("Reverse string=" + s2);
        
             
    }
    
}

Output of Java String Reverse Program

Enter a String to Reverse: Hello Java
Original string=Hello Java
Reverse string=avaJ olleH

Enter a String to Reverse: Cricket Match
Original string=Cricket Match
Reverse string=hctaM tekcirC