ClassValue in Java 7

Question

While browsing the Java 7 API documentation I stumbled upon the new class java.lang.ClassValue with the following rather minimal documentation:

Lazily

Answer 1

The best explanation of the purpose of this class is that it solves Java Bug 6389107

There are many use cases where one wants to essentially have a Map, T> for some reason, but this causes all sorts of trouble since Class objects will then not be GC-able until the Map is. WeakHashMap, T> doesn't solve the problem because very frequently, T references the class.

The bug above goes into a much more detailed explanation and contains example projects/code that face this problem.

ClassValue is the answer to this problem. A thread-safe, classloader loading/unloading safe way to associate data with a Class.