java并发初探ReentrantWriteReadLock

ReenWriteReadLock类的优秀博客

ReentrantReadWriteLock读写锁详解
Java多线程系列--“JUC锁”08之 共享锁和ReentrantReadWriteLock

ReentrantWriteReadLock类实现

@startuml
interface Lock
interface ReadWriteLock
class ReentrantReadWriteLock{
Sync sync
ReentrantReadWriteLock.ReadLock readerLock;
ReentrantReadWriteLock.WriteLock writerLock;
}
ReadWriteLock <|-- ReentrantReadWriteLock
ReentrantReadWriteLock --o ReadLock
ReentrantReadWriteLock --o WriteLock
ReentrantReadWriteLock --o Sync
AbstractQueuedSynchronizer <|- Sync
Lock <|-- ReadLock
Lock <|-- WriteLock
@enduml

特点

ReentrantWriteReadLock内部有读锁和写锁。
写锁是独占锁
当前线程持有写锁，其他线程只能等待
当其他线程拥有对象的写锁或者读锁，当前线程等待获取写锁
读锁是共享锁
没有其他线程的写锁，当前线程可以获取读锁

使用例子

package com.java.javabase.thread.base.concurrent.lock;import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.extern.slf4j.Slf4j;import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;@Slf4j
public class ReentranReadWriteLockTest {/*** @author* @version* @since*/public static void main(String[] args) {ReentranReadWriteLockTest test =new ReentranReadWriteLockTest();User user =test.new User("jack",test.new Count("001",1000));for(int i=0;i<3;i++){user.printCash();user.setCash(1000);}}@Data@AllArgsConstructor@NoArgsConstructorclass Count {private String id;private int cash;}@Dataclass User {private String name;private Count count;private ReadWriteLock readWriteLock;public User(String name, Count count) {this.name = name;this.count = count;this.readWriteLock = new ReentrantReadWriteLock();}public void setCash(final int cash) {new Thread() {@Overridepublic void run() {readWriteLock.writeLock().lock();try {log.info("thread {} :user {} set  cash {} start",Thread.currentThread().getName(), name, cash);Thread.sleep(1000);log.info("thread {} :user {} current  cash = {}",Thread.currentThread().getName(), name, count.getCash());count.setCash(cash);log.info("thread {} :user {} set  cash {} end",Thread.currentThread().getName(), name, cash);} catch (InterruptedException e) {e.printStackTrace();}finally {readWriteLock.writeLock().unlock();}}}.start();}public void printCash() {new Thread() {@Overridepublic void run() {try {readWriteLock.readLock().lock();log.info("thread {} :user {} get  cash start", Thread.currentThread().getName(), name);log.info("thread {} :user {} current  cash = {}",Thread.currentThread().getName(), name, count.getCash());Thread.sleep(1000);log.info("thread {} :user {} get  cash end", Thread.currentThread().getName(), name);} catch (InterruptedException e) {e.printStackTrace();} finally {readWriteLock.readLock().unlock();}}}.start();}}
}

例子结果

2019-08-09 10:49:15,618   [Thread-0] INFO  ReentranReadWriteLockTest  - thread Thread-0 :user jack get  cash start
2019-08-09 10:49:15,618   [Thread-0] INFO  ReentranReadWriteLockTest  - thread Thread-0 :user jack current  cash = 1000
2019-08-09 10:49:16,618   [Thread-0] INFO  ReentranReadWriteLockTest  - thread Thread-0 :user jack get  cash end
2019-08-09 10:49:16,618   [Thread-1] INFO  ReentranReadWriteLockTest  - thread Thread-1 :user jack set  cash 1000 start
2019-08-09 10:49:17,618   [Thread-1] INFO  ReentranReadWriteLockTest  - thread Thread-1 :user jack current  cash = 1000
2019-08-09 10:49:17,618   [Thread-1] INFO  ReentranReadWriteLockTest  - thread Thread-1 :user jack set  cash 1000 end
2019-08-09 10:49:17,618   [Thread-4] INFO  ReentranReadWriteLockTest  - thread Thread-4 :user jack get  cash start
2019-08-09 10:49:17,618   [Thread-2] INFO  ReentranReadWriteLockTest  - thread Thread-2 :user jack get  cash start
2019-08-09 10:49:17,618   [Thread-4] INFO  ReentranReadWriteLockTest  - thread Thread-4 :user jack current  cash = 1000
2019-08-09 10:49:17,618   [Thread-2] INFO  ReentranReadWriteLockTest  - thread Thread-2 :user jack current  cash = 1000
2019-08-09 10:49:18,618   [Thread-4] INFO  ReentranReadWriteLockTest  - thread Thread-4 :user jack get  cash end
2019-08-09 10:49:18,618   [Thread-2] INFO  ReentranReadWriteLockTest  - thread Thread-2 :user jack get  cash end
2019-08-09 10:49:18,618   [Thread-5] INFO  ReentranReadWriteLockTest  - thread Thread-5 :user jack set  cash 1000 start
2019-08-09 10:49:19,617   [Thread-5] INFO  ReentranReadWriteLockTest  - thread Thread-5 :user jack current  cash = 1000
2019-08-09 10:49:19,617   [Thread-5] INFO  ReentranReadWriteLockTest  - thread Thread-5 :user jack set  cash 1000 end
2019-08-09 10:49:19,617   [Thread-3] INFO  ReentranReadWriteLockTest  - thread Thread-3 :user jack set  cash 1000 start
2019-08-09 10:49:20,617   [Thread-3] INFO  ReentranReadWriteLockTest  - thread Thread-3 :user jack current  cash = 1000
2019-08-09 10:49:20,617   [Thread-3] INFO  ReentranReadWriteLockTest  - thread Thread-3 :user jack set  cash 1000 end