04. Reverse String

import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String input = scanner.nextLine(),
                reverseString = "";

        for (int i = input.length() - 1; i >= 0; i--){
            reverseString += input.charAt(i);
        }

        System.out.println(reverseString);
    }
}

Solution with methods:

import java.util.Scanner;
import java.io.*;

class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String reverseString = new StringBuilder(scanner.nextLine()).reverse().toString();

        System.out.println(reverseString);
    }
}

OR:

import java.util.Scanner;
import java.io.*;

class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.println(new StringBuilder(scanner.nextLine()).reverse().toString());
    }
}