标签：ini current imp obj ati ons sleep 机制 nts
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。wait方法调用，可以让当前线程进入等待状态，对该对象的notify方法调用，则可以让在该对象上进入wait等待状态的一个随机线程被唤醒继续工作。notifyall则可以调用所有。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<Thread> getBlockedThreads();
}
class BooleanLock implements Lock
{
private Thread currentThread;
private boolean locked = false;
private final List<Thread> 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<Thread> getBlockedThreads() {
return Collections.unmodifiableList(blockedList);
}
}
public class notifyWaitStudy {
}
标签：ini current imp obj ati ons sleep 机制 nts
原文地址：http://blog.51cto.com/ggwhsd/2345002
