Why not change strings in java(w/ reflection)

//This is what happens if you change a string using reflection.(Only for interned(hardcoded) strings)
import java.lang.reflect.Field;

public class MutateString {

    public static final String addr = "ADDR_PLACEH";

    //Results:
    //Initial: ADDR_PLACEH
    //From var: 192.168.1.1
    //Hardcoded: 192.168.1.1
    //Substring: ADDR_PLACEH
    //Equals test: true
    //Equals test with substring: false
    public static void main(String[] args) {
        System.out.print("Initial: "); System.out.println(addr);
        editIntStr("ADDR_PLACEH", "192.168.1.1");
        System.out.print("From var: "); System.out.println(addr);
        System.out.print("Hardcoded: "); System.out.println("ADDR_PLACEH");
        System.out.print("Substring: "); System.out.println("ADDR_PLACE" + "H".substring(0));
        System.out.print("Equals test: "); System.out.println("ADDR_PLACEH".equals("192.168.1.1"));
        System.out.print("Equals test with substring: ");  System.out.println(("ADDR_PLACE" + "H".substring(0)).equals("192.168.1.1"));
    }

    public static void editIntStr(String from, String to) {
        Field f = null;
        try {
            f = String.class.getDeclaredField("value");
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
        f.setAccessible(true);
        try {
            f.set(from, to.toCharArray());
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
    }
}