fork download 
  1. import java.util.*;
  2. import java.lang.reflect.*;
  3.  
  4. enum Color {RED, BLUE, GREEN};
  5.  
  6. class Example {
  7.     public static void main(String[] args) throws Exception {
  8.         // use the Field at least once so it creates and caches accessors
  9.         // with the final modifier
  10.         System.out.println(Arrays.toString((Object[]) getValuesField(Color.class).get(null)));
  11.  
  12.         // now throws IllegalAccessException, because removing
  13.         // the final modifier has no effect (IllegalAccessException
  14.         // is thrown by the field accessor)
  15.         try {
  16.             setEnumsArray(Color.class, Color.RED, Color.RED, Color.RED);
  17.         } catch (IllegalAccessException x) {
  18.             System.out.println(x);
  19.             System.out.println("    at " + x.getStackTrace()[0]);
  20.         }
  21.  
  22.         // clear accessors
  23.         clearFieldAccessors(getValuesField(Color.class));
  24.         // now it works
  25.         setEnumsArray(Color.class, Color.RED, Color.RED, Color.RED);
  26.  
  27.         System.out.println(Arrays.toString(Color.values()));
  28.     }
  29.  
  30.     static Field getValuesField(Class<?> c) throws Exception {
  31.         Field f = c.getDeclaredField("$VALUES");
  32.         f.setAccessible(true);
  33.         return f;
  34.     }
  35.  
  36.     static <E extends Enum<E>> void setEnumsArray(Class<E> ec, E... e) throws Exception {
  37.         Field field = getValuesField(ec);
  38.         Field modifiersField = Field.class.getDeclaredField("modifiers");
  39.         field.setAccessible(true);
  40.         modifiersField.setAccessible(true);
  41.         modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);
  42.         field.set(ec, e);
  43.     }
  44.  
  45.     static void clearFieldAccessors(Field field)
  46.             throws ReflectiveOperationException {
  47.         Field fa = Field.class.getDeclaredField("fieldAccessor");
  48.         fa.setAccessible(true);
  49.         fa.set(field, null);
  50.  
  51.         Field ofa = Field.class.getDeclaredField("overrideFieldAccessor");
  52.         ofa.setAccessible(true);
  53.         ofa.set(field, null);
  54.  
  55.         Field rf = Field.class.getDeclaredField("root");
  56.         rf.setAccessible(true);
  57.         Field root = (Field) rf.get(field);
  58.         if (root != null) {
  59.             clearFieldAccessors(root);
  60.         }
  61.     }
  62. }
Success #stdin #stdout 0.1s 27872KB
comments (?)
stdin 
Standard input is empty
stdout 
[RED, BLUE, GREEN]
java.lang.IllegalAccessException: Can not set static final [LColor; field Color.$VALUES to [LColor;
    at sun.reflect.UnsafeFieldAccessorImpl.throwFinalFieldIllegalAccessException(UnsafeFieldAccessorImpl.java:76)
[RED, RED, RED]
https://ideone.com/JhBCb2
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!