为什么锁被捕获到局部变量 [英] Why is lock captured to a local variable

问题描述

在Java JRE中，我看到了

In java JRE I saw the code

private final ReentrantLock lock;
public E poll() {
        final ReentrantLock lock = this.lock;
        lock.lock();

为什么锁被捕获到私有变量?我只希望

Why is lock captured to a private variable? I would expect simply

public E poll() {
        lock.lock();

推荐答案

主要是为了确保最佳性能.尽管这是真正的微优化，但它可能是对性能敏感的代码，您也可以这样做.

Primarily it is to ensure maximum performance. Although this is a real micro-optimisation, it's probably in performance-sensitive code, and you might as well make it.

您还需要非常小心，确保所使用的锁引用不会发生变化.确保将字段设置为final，但是采用final本地引用是本地显式的.

You also need to be very careful that the lock reference you are using doesn't mutate. Sure make the field final, but taking a final local reference is locally explicit.

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