5000字 | 详解 Java 中的 21 种锁

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序号	锁名称	应用
1	乐观锁	CAS
2	悲观锁	synchronized、vector、hashtable
3	自旋锁	CAS
4	可重入锁	synchronized、Reentrantlock、Lock
5	读写锁	ReentrantReadWriteLock，CopyOnWriteArrayList、CopyOnWriteArraySet
6	公平锁	Reentrantlock(true)
7	非公平锁	synchronized、reentrantlock(false)
8	共享锁	ReentrantReadWriteLock中读锁
9	独占锁	synchronized、vector、hashtable、ReentrantReadWriteLock中写锁
10	重量级锁	synchronized
11	轻量级锁	锁优化技术
12	偏向锁	锁优化技术
13	分段锁	concurrentHashMap
14	互斥锁	synchronized
15	同步锁	synchronized
16	死锁	相互请求对方的资源
17	锁粗化	锁优化技术
18	锁消除	锁优化技术

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占用处理器的时间，如果占用的时间很长，会白白消耗处理器资源，而不会做任何有价值的工作，带来性能的浪费。因此自旋等待的时间必须有一定的限度，如果自旋超过了限定的次数仍然没有成功获得锁，就应当使用传统的方式去挂起线程。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"自旋","attrs":{}}],"attrs":{}},{"type":"text","text":"次数默认值：10次，可以使用参数-XX:PreBlockSpin来自行更改。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"自适应","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"自旋","attrs":{}}],"marks":[{"type":"strong"}],"attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"：","attrs":{}},{"type":"text","text":" 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