Main.java

package modern.challenge;

import java.lang.reflect.Field;

public class Main {

    // Run this code in JDK 8
    
    public static void main(String[] args) 
            throws NoSuchFieldException, IllegalAccessException {

        String user = "guest";
        System.out.println("User is of type: " + user);

        Class<String> type = String.class;
        Field field = type.getDeclaredField("value");
        field.setAccessible(true);

        char[] chars = (char[]) field.get(user);

        chars[0] = 'a';
        chars[1] = 'd';
        chars[2] = 'm';
        chars[3] = 'i';
        chars[4] = 'n';

        System.out.println("User is of type: " + user);
    }

}