Question

Write a method that accepts a String object as an argument and displays its contents backward. For instance, if the string argument is "gravity" the method should display "ytivarg". Demonstrate the method in a program that asks the user to input a string and then prints out the result of passing the string into the method.

Sample Run
java BackwardString

Enter·a·string:Hello·world↵
dlrow·olleH↵

Answer 1

I have created a java application named BackwardString in NetBeans IDE.

package backwardstring;

import java.lang.*;
import java.io.*;
import java.util.*;
import java.util.Scanner;
public class BackwardString {

    public static String reverse(String s){
        
        //convert the string into charater array
        char[] arr1 = s.toCharArray();
        
        //declare array to store the reversed character
        char[] arr2 = new char[arr1.length];
        
        int j = 0;
        
        //loop start from last charater in arr1 and store it in first position in arr2
        //store all element of arr1 from last into arr2 from starting
        for (int i = arr1.length - 1; i >= 0; i--){
            arr2[j] = arr1[i];
            j++;
        }
        
        //convert the character array to string and store it in a result
        String result = String.valueOf(arr2);
        
        //return result
        return result;
                
    }
    
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str, rev;
        
        //prompts user to enter string
        System.out.print("Enter a string:");
        str = sc.nextLine();
        
        //call reverse method and store the result in rev
        rev = reverse(str);
        
        //print rev
        System.out.println(rev);
        
    }
    
}

OUTPUT: