java.util.concurrent package includes a number of additions to the Java Collections Framework. These are most easily categorized by the collection interfaces provided:
BlockingQueuedefines a first-in-first-out data structure that blocks or times out when you attempt to add to a full queue, or retrieve from an empty queue.
ConcurrentMapis a subinterface of
java.util.Mapthat defines useful atomic operations. These operations remove or replace a key-value pair only if the key is present, or add a key-value pair only if the key is absent. Making these operations atomic helps avoid synchronization. The standard general-purpose implementation of
ConcurrentHashMap, which is a concurrent analog of
ConcurrentNavigableMapis a subinterface of
ConcurrentMapthat supports approximate matches. The standard general-purpose implementation of
ConcurrentSkipListMap, which is a concurrent analog of
All of these collections help avoid Memory Consistency Errors by defining a happens-before relationship between an operation that adds an object to the collection with subsequent operations that access or remove that object.