Question

Write a program to take a string as input and output its reverse.
Write the program in java.​

Answer 1

Answer:

import java.util.Scanner;

public class Main{

    public static void main(String[] args) {

       Scanner scanner = new Scanner(System.in);

       System.out.print("Input a string: ");

       char[] letters = scanner.nextLine().toCharArray();

       System.out.print("Reverse string: ");

       for (int i = letters.length - 1; i >= 0; i--) {

           System.out.print(letters[i]);

       }

       System.out.print("\n");

   }

}

Explanation:

Answer 2

Answer:

Using Java, the co‎de goes like -

import java.util.*;

public class Reverse_String {

   public static void main(String args[])  {

       System.out.print("Enter a String: ");

       String original_string,reversed_string="";

       original_string=(new Scanner(System.in)).nextLine();

       for(int i=original_string.length()-1;i>=0;i--)

           reversed_string+=original_string.charAt(i);

       System.out.println("Original String: "+original_string);

       System.out.println("Reversed String: "+reversed_string);

   }

}

Logic:

Logic is very easy. Consider a string - "Hello"

Length of string = 5

Now, let us write the index of each character in the string. Note that index value starts with 0.

$\dag\ \boxed{\begin{array}{c|c|c|c|c|c}\tt\underline{Char}:&\tt H&\tt e&\tt l&\tt l&\tt o\\ \tt\underline{Index}:&\tt0&\tt1&\tt2&\tt3&\tt4\end{array}}$

So, index value range is - (0 to length(string) - 1)

• Here, a loop is created that iterates in the range i > length(original_string) - 1 to 0 so as to access the characters present in the string from last to first.
• To calculate the length of string, the length() function is used and to access the character at specific index, the charAt() function is used.
• Using charAt() function, we will access the characters present in the string from backwards and concatenate them. The resultant string is the reversed one of the original.

See the attachment.