* <p>This class is conditionally thread-safe (see Item 70, Effective Java second edition). To
* properly use this class across multiple threads, you will need to add some external
* synchronization. For example:
* <p>This class is conditionally thread-safe (see Item 70, Effective Java second edition). To
* properly use this class across multiple threads, you will need to add some external
* synchronization. For example: