JakeWharton/DiskLruCache — pull request #56 by Wavesonics (2014-02-10 19:56:02+00:00)
Title: Replaced synchronize's with ReentrantReadWriteLock & added contains() method

This PR removes all synchronized statements in favor of a ```ReentrantReadWriteLock```. This allows read operations to not block each other, but write operations to block everything (*the way synchronized was working previously*).

With the addition of a simple ```contains()``` method, it is now super cheap to check if an image exists in the cache.