java 多线程 读写锁

利用读写锁（ReentrantReadWriteLock） 可实现对临界资源多线程时读写控制

 

class M

{

private static Map<Integer,String> map = new HashMap<Integer,String>();  

private static M m = new M(map);

public static M getInstance()

{

return m;

}

    private final ReadWriteLock lock = new ReentrantReadWriteLock();  

    private final Lock r = lock.readLock();  

    private final Lock w = lock.writeLock();  

    public M(Map<Integer,String> map) {  

        this.map = map;  

    }  

    public String put(Integer key, String value) {  

     System.out.println("waiting put");

        w.lock();  

        try { 

         System.out.println("processing put");

         try {

Thread.sleep(5000l);

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

            return map.put(key, value);  

        } finally {  

            w.unlock();  

        }  

    }  

 

    public String get(Object key) {  

     System.out.println("waiting get");

        r.lock();  

        try {

         System.out.println("processing get");

         try {

Thread.sleep(5000l);

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

            return map.get(key);  

        } finally {  

            r.unlock();  

        }  

    }  

  

}

public class CheckCloneable implements Runnable

{

private int i;

private boolean get;

CheckCloneable(int i,boolean get)

{

this.i = i;

this.get = get;

}

public void run()

{

M m = M.getInstance();

if(get)

{

m.get(new Integer(1));

}

else

{

m.put(new Integer(1), "1");

}

}

public static void main(String[] args)

{

boolean getfirst = false;

CheckCloneable c = new CheckCloneable(0,getfirst);

Thread t = new Thread(c);

t.start();

CheckCloneable c2 = new CheckCloneable(1,getfirst);

Thread t2 = new Thread(c2);

t2.start();

}

}