Reflection and String immutability

One very powerful but risky tool is Reflection. Using reflection, you can break almost everything - from encapsulation to immutability

Here is a piece of code which breaks immutability of String class

import java.lang.reflect.Field;


public class MutableString {

     public static void main(String[] args) throws Exception {
          String someString = "IMMUTABLE";

          Field field = Class.forName("java.lang.String").getDeclaredField("value");
          field.setAccessible(true);
          char[] value = (char []) field.get(someString);

          String anotherString = "NOTREALLY";

          for (int i=0; i<value.length; i++){
               char c = anotherString.toCharArray()[i];
               value[i]=c;
          }

          System.out.println(someString); // prints NOTREALLY
          System.out.println("IMMUTABLE"); // WTF !!! prints NOTREALLY  
      }
 }

Output:

NOTREALLY
NOTREALLY