ReentrantReadWriteLock

使用ReentrantLock构建简单的读写锁

package com.dwz.locks;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;

public class ReadWriteLockExample {
    private final static ReentrantLock lock = new ReentrantLock();
    private final static List<Long> data = new ArrayList<>();
    
    public static void main(String[] args) throws InterruptedException {
        Thread thread1 = new Thread(ReadWriteLockExample::write);
        thread1.start();
        
        TimeUnit.SECONDS.sleep(1);
        
        Thread thread2 = new Thread(ReadWriteLockExample::read);
        thread2.start();
    }
    
    public static void write() {
        try {
            lock.lock();
            data.add(System.currentTimeMillis());
            TimeUnit.SECONDS.sleep(5);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
    
    public static void read() {
        try {
            lock.lock();
            data.forEach(System.out::println);
            TimeUnit.SECONDS.sleep(5);
            System.out.println(Thread.currentThread().getName() + "====================");
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
    
}

使用ReentrantReadWriteLock

package com.dwz.locks;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
 *    使用ReentrantReadWriteLock解决读写安全问题以及同时读不需要加锁问题
 *
 *    write write false
 *    write read  false
 *    read  write false
 *    read  read  true
 */
public class ReadWriteLockExample2 {
    private final static ReentrantReadWriteLock readWriteLock = new ReentrantReadWriteLock();
    
    private final static Lock readLock = readWriteLock.readLock();
    
    private final static Lock writeLock = readWriteLock.writeLock();
    
    private final static List<Long> data = new ArrayList<>();
    
    public static void main(String[] args) throws InterruptedException {
        Thread thread1 = new Thread(ReadWriteLockExample::read);
        thread1.start();
        
        TimeUnit.SECONDS.sleep(1);
        
        Thread thread2 = new Thread(ReadWriteLockExample::read);
        thread2.start();
    }
    
    public static void write() {
        try {
            writeLock.lock();
            data.add(System.currentTimeMillis());
            TimeUnit.SECONDS.sleep(5);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            writeLock.unlock();
        }
    }
    
    public static void read() {
        try {
            readLock.lock();
            data.forEach(System.out::println);
            TimeUnit.SECONDS.sleep(5);
            System.out.println(Thread.currentThread().getName() + "====================");
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            readLock.unlock();
        }
    }
}