String不改变地址的前提下更改值

public static void main(String[] args) throws Exception {
    String a = "a";
    System.out.println("修改前" + a );
    Field value = a.getClass().getDeclaredField("value");
    value.setAccessible(true);
    value.set(a , "1".toCharArray());
    System.out.println("修改后" + a);
}