Java™ How To Program (Early Objects), Tenth Edition

16.13 Synchronized Collections

In Chapter 23, we discuss multithreading. Except for Vector and Hashtable, the collections in the collections framework are unsynchronized by default, so they can operate efficiently when multithreading is not required. Because they’re unsynchronized, however, concurrent access to a Collection by multiple threads could cause indeterminate results or fatal errors—as we demonstrate in Chapter 23. To prevent potential threading problems, synchronization wrappers are used for collections that might be accessed by multiple threads. A wrapper object receives method calls, adds thread synchronization (to prevent concurrent access to the collection) and delegates the calls to the wrapped collection object. The Collections ...