java并发初探ReentrantWriteReadLock

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
    @NoArgsConstructor
    class Count {
        private String id;
        private int cash;
    }

    @Data
    class 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() {
                @Override
                public 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() {
                @Override
                public 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