java 5 ReadWriteLock

import java.util.ArrayList;

import java.util.List;

import java.util.concurrent.locks.ReadWriteLock;

import java.util.concurrent.locks.ReentrantReadWriteLock;



public class ReadWriteLockTest

{

    private static List<String> list = new ArrayList<String>();

    public static void main(String[] args)

    {

        for(int i = 0; i < 10; i++)

        {

            list.add("init - " + i);

        }

        new Thread(new Runnable()

        {

            public void run()

            {

                try

                {

                    ReadWriteLockTest.add();

                }

                catch (Exception e)

                {

                    e.printStackTrace();

                }

            }

        }).start();

        new Thread(new Runnable()

        {

            public void run()

            {

                try

                {

                    ReadWriteLockTest.get();

                }

                catch (Exception e)

                {

                    e.printStackTrace();

                }

            }

        }).start();

    }

    

    private static ReadWriteLock lock = new ReentrantReadWriteLock();

    private static void add() throws Exception

    {

        for(int i = 0; i < 10; i++)

        {

            lock.writeLock().lock();

            list.add("add-" + i);

            lock.writeLock().unlock();

            System.out.println("add " + i);

            Thread.sleep(500);

        }

    }

    

    private static void get() throws Exception

    {

        lock.readLock().lock();

        for(String str : list)

        {

            System.out.println("get- " + str);

            Thread.sleep(500);

        }

        lock.readLock().unlock();

    }

}

上面有2个线程同时对list变量读写，如果不使用读写锁，则程序会抛出异常。

多个读锁不互斥，读锁也写锁互斥，写锁与写锁互斥。