Is it possible to create a memory leak with Java

Question

If possible, what would be a good example for it?

Answer 1

Here's a good way to create a memory leak in pure Java:

1.  a long-running thread  is created by the application
2. The thread loads a class via an (optionally custom) ClassLoader
3. The class allocates a large chunk of memory (e.g. new byte[1000000]), stores a strong reference to it in a static field, and then stores a reference to itself in a ThreadLocal
4. Allocating the extra memory is optional, but it will make the leak work that much faster
5. All references are cleared to the custom class or the ClassLoader  from which it was loaded
6. Repeat

This works because the ThreadLocal keeps a reference to the object, which keeps a reference to its Class, which in turn keeps a reference to its ClassLoader. The ClassLoader, in turn, keeps a reference to all the Classes it has loaded