CustomConcurrentHashMap - A framework for concurrent hash map implementations.

com.google.inject.internal.CustomConcurrentHashMap:
"A framework for concurrent hash map implementations."
"Retrieval operations (including java.util.Map.get(java.lang.Object)) generally do not block, so may overlap with update operations (including java.util.Map.put(java.lang.Object, java.lang.Object) and java.util.Map.remove(java.lang.Object))."
"Retrievals reflect the results of the most recently completed update operations holding upon their onset."
"For example, the following strategy emulates the behavior of java.util.concurrent.ConcurrentHashMap: ..."

Concurrency lessons from eBay engineers

On JavaOne Technical Sessions 2009 3 engineers from eBay speek about Java concurrency troubles/lessons that they learned.
- Lazy Initialization patern
- Holder pattern
- correct Double-Checked Locking pattern
- Interesting example: ConcurrentMap of AtomicInteger
- DateFormat, MessageDigest, CharsetEncoder/CharsetDecoder - not thread safe
- ThreadLocal pattern
- potential lock contention on Class.forName(...) when missing class
- SAXParserFactory.newInstance().newSAXParser() - potentially significant lock contention on META-INF
P.S. You MUST be resistered at Sun. Its easy.
P.P.S. And, Yes, eBay, Amazon and part of Google writed in Java:)