线程间进行通信，简单的方法可以有利用synchronized来同步某个数据标志，一个线程负责设置标志，另一个线程负责循环检测该标志，这种方法的好处时方便，但是需要轮训，消耗太多的cpu时间。那有人说，可以使用sleep，每sleep一毫秒，检测一次，这样就不用消耗太多cpu时间了，这种方法是不错，若是没有明显的低延迟要求，真的可以的。但若是对于sleep有时间要求呢，希望尽快，而不是一个固定时间呢，这时候就最好使用java提供的线程通信机制。

package Thread_03;import java.util.List;import java.util.Optional;import java.util.ArrayList;import java.util.Collections;import java.util.concurrent.TimeoutException;import static java.lang.Thread.currentThread;import static java.lang.System.currentTimeMillis;/* * 用synchronized 和 Object的对象的wait和notify。 来开发一个精简版的lock。 *  */interface Lock{    void lock() throws InterruptedException;    void lock(long mills) throws InterruptedException,TimeoutException;    void unlock();    List
    
      getBlockedThreads();}class BooleanLock implements Lock{    private Thread currentThread;    private boolean locked = false;    private final List
     
       blockedList = new ArrayList<>();    @Override    public void lock() throws InterruptedException {        synchronized(this)        {            while(locked)            {                if(!blockedList.contains(currentThread()))                    blockedList.add(currentThread());                this.wait();            }            blockedList.remove(currentThread());            this.locked = true;            this.currentThread = currentThread();        }    }    @Override    public void lock(long mills) throws InterruptedException, TimeoutException {        synchronized(this)        {            if(mills<0)            {                this.lock();            }            else            {                long remainingMills = mills;                long endMills = currentTimeMillis() + remainingMills;                while(locked)                {                    if(remainingMills <= 0)                        throw new TimeoutException("can not get lock : wait time out");                    if(!blockedList.contains(currentThread()))                        blockedList.add(currentThread());                    this.wait(remainingMills);                    remainingMills = endMills - currentTimeMillis();                }                blockedList.remove(currentThread());                this.locked = true;                this.currentThread = currentThread();            }        }    }    @Override    public void unlock() {        synchronized(this)        {            if(currentThread == currentThread())            {                this.locked = false;                //Optional.of("dd").ifPresent(System.out::println);                this.notifyAll();            }        }    }    @Override    public List
      
        getBlockedThreads() {        return Collections.unmodifiableList(blockedList);    }}public class notifyWaitStudy {}