本文共 2499 字，大约阅读时间需要 8 分钟。

0. 一个简单的工作者线程实现

• 我认为在涉及多线程/并发编程时，如果没有丰富的经验，则极易出错。所以应当优先使用 JDK 中提供的并发编程类。
• 必须留心共享变量的竞态条件。可能一不小心便会造成死锁。多思考，多分析。且代码尽量简洁，控制共享变量的操作/使用范围。

1. 代码如下：

import java.util.concurrent.atomic.AtomicInteger;public class Worker extends Thread {
   	private static final AtomicInteger counter = new AtomicInteger(1);	// 记录当前正在执行的 task， null 值则表示 worker 处于空闲状态（即 进入wait() 等待派发任务 task）	private volatile Runnable task;	private static final String NAME_PREFIX = "worker-";	private final String workerName;	private boolean isInterrupted = false;	private volatile boolean isRunning = false;	private volatile boolean isStarted = false;	private boolean isDestroyed = false;		public Worker(String name) {
   		this.workerName = NAME_PREFIX + counter.getAndIncrement() + (name == null ? "" : "-" + name);	}		public Worker() {
   		this(null);	}		public Worker(String name, Runnable task) {
   		this(name);		this.task = task;	}		public boolean doTask(Runnable task) {
   		if (task == null) {
   			throw new IllegalArgumentException("task must not be null.");		}		if (!isStarted && !isDestroyed) {
   			this.start();		}else if (isDestroyed) {
   			throw new IllegalStateException("this worker was destroyed.");		}		// 尝试减少锁的获取次数		if (this.task != null) {
   			return false;		}		return compareAndUpdate(null, task);	}	/** 比较然后更新 */	private synchronized boolean compareAndUpdate(Runnable old, Runnable update) {
   		if (this.task == old) {
   			this.task = update;			if (this.task != null) {
   				// 通知 worker 继续工作				this.notify();			}			return true;		}		return false;	}		public boolean isRunning() {
   		return this.isRunning;	}		public boolean isStarted() {
   		return this.isStarted;	}		public String getWorkerName() {
   		return workerName;	}		@Override	public void run() {
   		this.isStarted = true;		while(!isInterrupted) {
   			this.isRunning = true;			Runnable currentTask = task;			if (currentTask != null) {
   				currentTask.run();				compareAndUpdate(currentTask, null);			}else {
   				synchronized (this) {
   					try {
   						// 避免死锁						if (this.task != null) {
   							continue;						}else {
   														this.isRunning = false;							wait();						}					} catch (InterruptedException ignore) {
   						isInterrupted = true;						// 再次设置自身的中断状态						this.interrupt();					}				}			}		}		this.isStarted = false;		this.isDestroyed = true;	}		public void exit() {
   		this.isDestroyed = true;		this.isStarted = false;		this.interrupt();		System.out.println(getWorkerName() + " exited.");	}}

转载地址：http://tjlsi.baihongyu.com/