Concurrent Collections并发集合

The java.util.concurrent package includes a number of additions to the Java Collections Framework. java.util.concurrent包包括对java集合框架的许多添加。These are most easily categorized by the collection interfaces provided:这些最容易通过提供的集合接口进行分类：

• 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.定义先进先出数据结构，当您尝试添加到完整队列或从空队列检索时，该数据结构会阻塞或超时。
• ConcurrentMap is a subinterface of java.util.Map that defines useful atomic operations. 是java.util.Map的子接口，定义了有用的原子操作。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. 这些操作仅在密钥存在时删除或替换键值对，或仅在密钥不存在时添加键值对。Making these operations atomic helps avoid synchronization. 使这些操作原子化有助于避免同步。The standard general-purpose implementation of ConcurrentMap is ConcurrentHashMap, which is a concurrent analog of HashMap.ConcurrentMap的标准通用实现是ConcurrentHashMap，它是HashMap的并发模拟。
• ConcurrentNavigableMap is a subinterface of ConcurrentMap that supports approximate matches. 是ConcurrentMap的子接口，支持近似匹配。The standard general-purpose implementation of ConcurrentNavigableMap is ConcurrentSkipListMap, which is a concurrent analog of TreeMap.ConcurrentNavigableMap的标准通用实现是ConcurrentSkipListMap，它是TreeMap的并发模拟。

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.所有这些集合都通过定义将对象添加到集合的操作与访问或删除该对象的后续操作之间的“发生在之前”关系来帮助避免内存一致性错误。