多线程编程之ReentrantReadWriteLock

ReentrantLock是一个完全互斥排他的效果（和synchronized一样），但是这样有的时候会影响效率，就像两个线程同时读取一个数据，这样并不会产生线程不安全，如果使用ReentrantLock则会形成：先读线程一，然后读线程二，但是使用ReentrantReadWriteLock就可以避免这种情况。

读读共享：

package ReentrantReadWriteLock;import java.util.concurrent.locks.ReentrantReadWriteLock;//读读共享public class Service {    ReentrantReadWriteLock lock = new ReentrantReadWriteLock();    public void Method() {        try {            lock.readLock().lock();            System.out.println("线程"+Thread.currentThread().getName()+"在"+System.currentTimeMillis()+"获得线程");            Thread.sleep(10000);        }catch(InterruptedException e){            e.printStackTrace();        }finally {            lock.readLock().unlock();        }    }}package ReentrantReadWriteLock;public class Run {    public static void main(String[] args) {        Service service = new Service();        Runnable runnable = new Runnable() {            public void run() {                service.Method();            }        };        Thread threadA = new Thread(runnable);        Thread threadB = new Thread(runnable);        threadA.setName("A");        threadA.start();        threadB.setName("B");        threadB.start();    }}//输出：//线程B在1508554977877获得锁//线程A在1508554977877获得锁//几乎同一时间开始

写写互斥：

package ReentrantReadWriteLock;import java.util.concurrent.locks.ReentrantReadWriteLock;//写写互斥public class Service2 {    ReentrantReadWriteLock lock = new ReentrantReadWriteLock();    public void Method() {        try {            lock.writeLock().lock();            System.out.println("线程"+Thread.currentThread().getName()+"在"+System.currentTimeMillis()+"获得线程");            Thread.sleep(10000);        }catch(InterruptedException e){            e.printStackTrace();        }finally {            lock.writeLock().unlock();        }    }}package ReentrantReadWriteLock;//写写互斥public class Run2 {    public static void main(String[] args) {        Service2 service = new Service2();        Runnable runnable = new Runnable() {            public void run() {                service.Method();            }        };        Thread threadA = new Thread(runnable);        Thread threadB = new Thread(runnable);        threadA.setName("A");        threadA.start();        threadB.setName("B");        threadB.start();    }}//输出：//线程A在1508555054030获得线程//线程B在1508555064030获得线程//这个大约中间间隔了10秒钟

读写互斥:

package ReentrantReadWriteLock;import java.util.concurrent.locks.ReentrantReadWriteLock;public class Service3 {    private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();    public void read() {        try {            lock.readLock().lock();            System.out.println("线程"+Thread.currentThread().getName()+"在"+System.currentTimeMillis()+"获得锁");            Thread.sleep(10000);        }catch(InterruptedException e) {            e.printStackTrace();        }finally {            lock.readLock().unlock();        }    }    public void write() {        try {            lock.writeLock().lock();            System.out.println("线程"+Thread.currentThread().getName()+"在"+System.currentTimeMillis()+"获得锁");            Thread.sleep(10000);        }catch(InterruptedException e) {            e.printStackTrace();        }finally {            lock.writeLock().unlock();        }    }}package ReentrantReadWriteLock;public class Run3 {    public static void main(String[] args) {        Service3 service = new Service3();        Runnable runnableRead = new Runnable() {            public void run() {                service.read();            }        };        Runnable runnablewrite = new Runnable() {            public void run() {                service.write();            }        };        Thread threadA = new Thread(runnableRead);        threadA.setName("A");        threadA.start();        Thread threadB = new Thread(runnablewrite);        threadB.setName("B");        threadB.start();    }}//输出：//线程A在1508555152523获得锁//线程B在1508555162524获得锁//中间也间隔了10秒左右