package algs12;
import stdlib.*;
import java.lang.reflect.Field;
/* ***********************************************************************
 *  Compilation:  javac MutableString.java
 *  Execution:    java MutableString
 *
 *  Shows that Strings are mutable if you allow reflection.
 *
 *************************************************************************/

public class XMutableString {

	public static void main(String[] argv) {
		String s = "Immutable";
		String t = "Notreally";

		mutate(s, t);
		StdOut.println(t);

		// strings are interned so this doesn't print "Immutable"
		StdOut.println("Immutable");
	}

	// change the first min(|s|, |t|) characters of s to t
	public static void mutate(String s, String t) {
		try {
			Field val = String.class.getDeclaredField("value");
			Field off = String.class.getDeclaredField("offset");
			val.setAccessible(true);
			off.setAccessible(true);
			int offset   = off.getInt(s);
			char[] value = (char[]) val.get(s);
			for (int i = 0; i < Math.min(s.length(), t.length()); i++)
				value[offset + i] = t.charAt(i);
		}
		catch (Exception e) { e.printStackTrace(); }
	}

}