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Concurrency
Concurrent Collections
The
java.util.concurrent package includes a number of
additions to the Java Collections Framework. These are most easily
categorized by the collection interfaces provided:
-
BlockingQueue
defines 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.
-
ConcurrentMap
is a subinterface of
java.util.Map
that 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
ConcurrentMap is
ConcurrentHashMap, which is a concurrent analog of
HashMap.
-
ConcurrentNavigableMap
is a subinterface of ConcurrentMap that supports
approximate matches.
The standard general-purpose implementation of
ConcurrentNavigableMap is
ConcurrentSkipListMap, which is a concurrent analog of
TreeMap.
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.
