Synchronization同步

Threads communicate primarily by sharing access to fields and the objects reference fields refer to. 线程主要通过共享对字段和引用字段引用的对象的访问来进行通信。This form of communication is extremely efficient, but makes two kinds of errors possible: thread interference and memory consistency errors. 这种形式的通信非常有效，但可能导致两种错误：线程干扰和内存一致性错误。The tool needed to prevent these errors is synchronization.防止这些错误所需的工具是同步。

However, synchronization can introduce thread contention, which occurs when two or more threads try to access the same resource simultaneously and cause the Java runtime to execute one or more threads more slowly, or even suspend their execution. 但是，同步可能会引入线程争用，当两个或多个线程试图同时访问同一资源时，会发生争用，并导致Java运行时执行一个或多个线程的速度变慢，甚至暂停它们的执行。Starvation and livelock are forms of thread contention. 饥饿和活锁是线程争用的两种形式。See the section Liveness for more information.有关更多信息，请参阅活性一节。

This section covers the following topics:本节涵盖以下主题：

• Thread Interference describes how errors are introduced when multiple threads access shared data.线程干扰描述了当多个线程访问共享数据时如何引入错误。
• Memory Consistency Errors describes errors that result from inconsistent views of shared memory.内存一致性错误描述共享内存视图不一致导致的错误。
• Synchronized Methods describes a simple idiom that can effectively prevent thread interference and memory consistency errors.同步方法描述了一个简单的习惯用法，可以有效地防止线程干扰和内存一致性错误。
• Implicit Locks and Synchronization describes a more general synchronization idiom, and describes how synchronization is based on implicit locks.隐式锁和同步描述了一种更通用的同步习惯用法，并描述了同步是如何基于隐式锁的。
• Atomic Access talks about the general idea of operations that can't be interfered with by other threads.原子访问讨论了不受其他线程干扰的操作的一般概念。