StringReverseWithoutSubstring.java

// Reverse a String without using substring()

import java.util.Scanner;
import java.util.Stack;

public class StringReverseWithoutSubstring {

    public static void main(String []args) {

        Scanner scan = new Scanner(System.in);
        System.out.print("Enter string: ");
        String input = scan.nextLine();
        if (input.length() == 0) {
            System.out.println("Nothing was entered.");
        } else {
            System.out.printf("Reverse of \"%s\": ", input);
            reverseTheWord(input);
        }
    }

    public static void reverseTheWord(String word) {
        Stack<String> stack = new Stack<>();
        Stack<String> reversedString = new Stack<>();
        int index = 0;
        while (index < word.length()) {
            stack.push(String.valueOf(word.charAt(index)));
            index++;
        }

        while (!stack.isEmpty()) {
            reversedString.push(stack.pop());
        }

        reversedString.forEach(letter->{
            System.out.print(letter);
        });
    }

}

/* Sample Output
Enter string: pastebin
Reverse of "pastebin": nibetsap
*/