What is the best code troll you've ever seen?

Consider the following Java snippet:

Integer a = 100, b = 100;
System.out.println(a == b);
Integer c = 200, d = 200;
System.out.println(c == d);

The first line will print true, and the second one will print false. This happens because Java has an autoboxing cache for Integers with a default range of [-128, 127]. Any value within that range will be reused from the cache.
Java Integer Cache - Java Tutorial Blog

Now, what if you mess with the cache and randomize it? Anyone doing arithmetic with Integer will have a really hard time understanding what the hell is going on!

// Extract the IntegerCache through reflection
    Class<?> clazz = Class.forName(
      "java.lang.Integer$IntegerCache");
    Field field = clazz.getDeclaredField("cache");
    field.setAccessible(true);
    Integer[] cache = (Integer[]) field.get(clazz);
 
    // Rewrite the Integer cache
    for (int i = 0; i < cache.length; i++) {
      cache[i] = new Integer(
        new Random().nextInt(cache.length));
    }
 
    // Prove randomness
    for (int i = 0; i < 10; i++) {
      System.out.println((Integer) i);
    }
  }

This code snippet were written by Lukas Eder on Add Some Entropy to Your JVM. For him, it printed this

92
221
45
48
236
183
39
193
33
84

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from Quora http://ift.tt/2icBr17