非重入锁

计数

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

public class MyLockUnenter implements Lock{

    private boolean isLock = false;
    
    @Override
    public synchronized void lock() {
        // TODO Auto-generated method stub
        while (isLock) {
            try {
                wait();
            } catch (Exception e) {
                // TODO: handle exception
            }
        }
        isLock = true;
    }
    
    @Override
    public synchronized void unlock() {
        // TODO Auto-generated method stub
        isLock = false;
        notify();
    }
    
    @Override
    public void lockInterruptibly() throws InterruptedException {
        // TODO Auto-generated method stub  
    }
    @Override
    public boolean tryLock() {
        // TODO Auto-generated method stub
        return false;
    }
    @Override
    public boolean tryLock(long time, TimeUnit unit)
            throws InterruptedException {
        // TODO Auto-generated method stub
        return false;
    }
    @Override
    public Condition newCondition() {
        // TODO Auto-generated method stub
        return null;
    }
}

public class TestUnenter {

    Lock lock = new MyLockUnenter();
    private int value;
    private int getnum(){
        lock.lock();
        int a = value++;
        lock.unlock();
        return a;
    }
    
    public static void main(String[] args) {
        
        TestUnenter testUnenter = new TestUnenter();
        new Thread(new Runnable() {
            
            @Override
            public void run() {
                // TODO Auto-generated method stub
                while (true) {
                    System.out.println(Thread.currentThread().getName()+" "+testUnenter.getnum());
                }
            }
        }).start();
        
        new Thread(new Runnable() {
            
            @Override
            public void run() {
                // TODO Auto-generated method stub
                while (true) {
                    System.out.println(Thread.currentThread().getName()+" "+testUnenter.getnum());
                }
            }
        }).start();
        
    }
}

线程无限期等待示例

public class TestUnenter {

    Lock lock = new MyLockUnenter();
    public void a(){
        lock.lock();
        System.err.println("a");
        b();
        lock.unlock();
    }
    
    public void b(){
        lock.lock();
        System.err.println("b");
//      b();
        lock.unlock();
    }
    
    public static void main(String[] args) {
        
        TestUnenter testUnenter = new TestUnenter();
        new Thread(new Runnable() {
            
            @Override
            public void run() {
                // TODO Auto-generated method stub
                TestUnenter d = new TestUnenter();
                d.a();
            }
        }).start();     
    }
}

重入锁，类似于sychronized，不会有死锁情况

public class MyLock implements Lock{

    private boolean isLock = false;
    private Thread lockby = null;//被锁住的线程
    private int locknum ;//锁重入的次数
    
    @Override
    public synchronized void lock() {
        // TODO Auto-generated method stub
//      先判断是否有线程已经获得锁，判断当前线程是否为锁住的线程
        Thread current = Thread.currentThread();
        while (isLock&&current!=lockby) {
            try {
                wait();
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        lockby = current;
        isLock = true;
        locknum++;
    }
    
    @Override
    public synchronized void unlock() {
        // TODO Auto-generated method stub
//      判断当前线程是否为锁住的线程
        if (lockby == Thread.currentThread()) {
//          重入次数减去1
            locknum--;
//          当最后一个锁被释放
            if (locknum == 0) {
                isLock = false;
                notify();
            }
        }
        
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        // TODO Auto-generated method stub
        
    }

    @Override
    public boolean tryLock() {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit)
            throws InterruptedException {
        // TODO Auto-generated method stub
        return false;
    }

    

    @Override
    public Condition newCondition() {
        // TODO Auto-generated method stub
        return null;
    }

}