Android?线程死锁场景与优化解决

    //首先我们先定义两个final的对象锁.可以看做是共有的资源.
    final Object lockA = new Object();
    final Object lockB = new Object();
//生产者A

class  ProductThreadA implements Runnable{
    @Override
    public void run() {
//这里一定要让线程睡一会儿来模拟处理数据 ,要不然的话死锁的现象不会那么的明显.这里就是同步语句块里面,首先获得对象锁lockA,然后执行一些代码,随后我们需要对象锁lockB去执行另外一些代码.
        synchronized (lockA){
            //这里一个log日志
            Log.e("CHAO","ThreadA lock  lockA");
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            synchronized (lockB){
                //这里一个log日志
                Log.e("CHAO","ThreadA lock  lockB");
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

            }
        }
    }
}
//生产者B
class  ProductThreadB implements Runnable{
    //我们生产的顺序真好好生产者A相反,我们首先需要对象锁lockB,然后需要对象锁lockA.
    @Override
    public void run() {
        synchronized (lockB){
            //这里一个log日志
            Log.e("CHAO","ThreadB lock  lockB");
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            synchronized (lockA){
                //这里一个log日志
                Log.e("CHAO","ThreadB lock  lockA");
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

            }
        }
    }
}
    //这里运行线程
    ProductThreadA productThreadA = new ProductThreadA();
    ProductThreadB productThreadB = new ProductThreadB();

    Thread threadA = new Thread(productThreadA);
    Thread threadB = new Thread(productThreadB);
    threadA.start();
    threadB.start();

ExecutorService pool = Executors.newSingleThreadExecutor(); //使用一个线程数模拟
pool.submit(() -> {
        try {
            log.info("First");
             //上一个线程没有执行完，线程池没有线程来提交本次任务，会处于等待状态
            pool.submit(() -> log.info("Second")).get();
            log.info("Third");
        } catch (InterruptedException | ExecutionException e) {
           log.error("Error", e);
        }
   });

synchronized(lock){
  while(true){
   // do some slow things
  }
}

public class ThreadWatcher {
    public int A = 0;
    public static void main(String[] args) {
        final ThreadWatcher threadWatcher = new ThreadWatcher();
        WorkThread t = new WorkThread(threadWatcher);
        t.start();
        while (true) {
            if (threadWatcher.A == 1) {
                System.out.println("Main Thread exit");
                break;
            }
        }
    }
}

class WorkThread extends Thread {
    private ThreadWatcher threadWatcher;
    public WorkThread(ThreadWatcher threadWatcher) {
        super();
        this.threadWatcher = threadWatcher;
    }
    @Override
    public void run() {
        super.run();
        System.out.println("sleep 1000");
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        this.threadWatcher.A = 1;
        System.out.println("WorkThread exit");

    }
}

CountDownLatch latch = new CountDownLatch(6);
ExecutorService service = Executors.newFixedThreadPool(5); 
for(int i=0;i< 5;i++){
    
final int no = i+1;
Runnable runnable=new Runnable(){
    @Override 
    public void run(){
            try{
                Thread.sleep((long)(Math.random()*10000));
                System.out.println("No."+no+"准备好了。");
            }catch(InterruptedException e){
                e.printStackTrace();
            }finally{
                latch.countDown();
            }
    }
};
service.submit(runnable);
}
System.out.println("开始执行.....");
latch.await();
System.out.println("停止执行");

public class RemovableTask implements Runnable {
    private static final String TAG = "RemovableTask";
    private Runnable target  = null;
    private Object lock = new Object();

    public RemovableTask(Runnable task) {
        this.target = task;
    }

    public static RemovableTask warp(Runnable r) {
        return new RemovableTask(r);
    }

    @Override
    public void run() {
        Runnable task;
        synchronized (this.lock) {
            task = this.target;
        }
        if (task == null) {
            MLog.d(TAG,"-cancel task-");
            return;
        }
        task.run();
    }

    public void dontRunIfPending() {
        synchronized (this.lock) {
            this.target = null;
        }
    }
}

public void purgHotSongRunnable() {
    for (RemovableTask r : pendingTaskLists){
        r.dontRunIfPending();
    }
}