推荐一个好的网站：，上面全是各种大牛原创或编译的并发编程文章。
Semaphore(信号量) 控制并发资源
例子：多个线程抢几个打印机的使用权
import org.junit.Test;import java.util.concurrent.Semaphore;import java.util.concurrent.TimeUnit;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;/** * Created by fengzp on 16/6/30. */public class SemaphoreDemo { @Test public void test() throws InterruptedException { PrintQueue printQueue = new PrintQueue(); int threadCount = 10; Thread thread[] = new Thread[threadCount]; for (int i = 0; i < threadCount; i++) { thread[i] = new Thread(new Job(printQueue), "Thread" + i); } for (int i = 0; i < threadCount; i++) { thread[i].start(); } TimeUnit.SECONDS.sleep(10); } public class Job implements Runnable { private PrintQueue printQueue; public Job(PrintQueue printQueue) { this.printQueue = printQueue; } public void run() { System.out.printf("%s: Going to print a job\n", Thread.currentThread().getName()); printQueue.printJob(new Object()); System.out.printf("%s: The document has been printed\n", Thread.currentThread().getName()); } } class PrintQueue { private boolean freePrinters[];//用来存放打印机的状态，true表示空闲，false表示正在打印 private Lock lockPrinters;//增加了锁，保证多个线程，只能获取得锁，才能查询哪台打印机空闲的 private final Semaphore semaphore; private final int printerNum = 3;//假设有3台打印机 public PrintQueue() { semaphore = new Semaphore(printerNum); freePrinters = new boolean[printerNum]; for (int i = 0; i < printerNum; i++) { freePrinters[i] = true;//初始化时，默认所有打印机都空闲 } lockPrinters = new ReentrantLock(); } private int getPrinter() { int ret = -1; try { lockPrinters.lock();//先加锁，保证1次只能有1个线程来获取空闲的打印机 for (int i = 0; i < freePrinters.length; i++) { //遍历所有打印机的状态，发现有第1个空闲的打印机后，领取号码， // 并设置该打印机为繁忙状态（因为马上就要用它） if (freePrinters[i]) { ret = i; freePrinters[i] = false; break; } } } catch (Exception e) { e.printStackTrace(); System.out.println(Thread.currentThread().getName() + "error"); } finally { //最后别忘记了解锁，这样后面的线程才能上来领号 lockPrinters.unlock(); } return ret; } public void printJob(Object document) { try { semaphore.acquire();//取得对共享资源的访问权（即拿到了钥匙）） int assignedPrinter = getPrinter();//领号 long duration = (long) (1 + Math.random() * 10); System.out.printf("%s: PrintQueue: Printing a Job in Printer%d during %d seconds\n", Thread.currentThread().getName(), assignedPrinter, duration); Thread.sleep(duration); freePrinters[assignedPrinter] = true;//打印完以后，将该打印机重新恢复为空闲状态 } catch (InterruptedException e) { e.printStackTrace(); System.out.println(Thread.currentThread().getName() + "error"); } finally { semaphore.release();//钥匙用完了，要还回去，这样其它线程才能继续有序的拿到钥匙，访问资源 } } }}
CyclicBarrier(等待多个线程执行完成后再后续处理)
import org.junit.Test;import java.util.concurrent.BrokenBarrierException;import java.util.concurrent.CyclicBarrier;/** * Created by fengzp on 16/6/30. */public class CyclicBarrierDemo { @Test public void test() throws BrokenBarrierException, InterruptedException { final int threadNum = 10; CyclicBarrier cb = new CyclicBarrier(threadNum + 1);//注意：10个子线程 + 1个主线程 for (int i = 0; i < threadNum; i++) { new Thread(new MyRunable(cb, i)).start(); } cb.await(); System.out.println("-----------\n所有thread执行完成！"); } static class MyRunable implements Runnable { CyclicBarrier _cb; int _i = 0; public MyRunable(CyclicBarrier cb, int i) { this._cb = cb; this._i = i; } @Override public void run() { try { Thread.sleep((long) (Math.random() * 100)); System.out.println("thread " + _i + " done，正在等候其它线程完成..."); _cb.await(); } catch (Exception e) { e.printStackTrace(); } } }}
Quere(队列，先进先出)
JDK7提供了以下7个阻塞队列：
ArrayBlockingQueue ：由数组结构组成的有界阻塞队列。
LinkedBlockingQueue ：由链表结构组成的有界阻塞队列。PriorityBlockingQueue ：支持优先级排序的无界阻塞队列。DelayQueue：使用优先级队列实现的无界阻塞队列。SynchronousQueue：不存储元素的阻塞队列。LinkedTransferQueue：链表结构组成的无界阻塞队列。LinkedBlockingDeque：链表结构组成的双向阻塞队列。阻塞队列提供了下列四种处理方法:
| 方法\处理方式 | 抛出异常 | 返回true/false | 一直阻塞 | 超时退出 |
|---|---|---|---|---|
| 插入方法 | add(e) | offer(e) | put(e) | offer(e,time,unit) |
| 移除方法 | remove() | poll() | take() | poll(time,unit) |
| 检查方法 | element() | peek() |
这4类方法中，在队列已满（或为空）的情况下，有些会抛出异常，有些则返回true/false，有些则一直阻塞，还有些则可以设置超时时间，时间到了后，自动退出阻塞状态，实际项目中可根据需要选取适合的方法。
例子：模拟生产者-消费者，1个生产者，3个消费者
import org.junit.Test;import java.util.concurrent.ArrayBlockingQueue;/** * Created by fengzp on 16/6/30. */public class QueueDemo { private static final int queueSize = 3; private static final ArrayBlockingQueue queue = new ArrayBlockingQueue<>(queueSize); private static final int produceSpeed = 2000;//生产速度(越小越快) private static final int consumeSpeed = 10;//消费速度(越小越快) public static void main(String[] args) { Thread producer = new Producer(); Thread consumer = new Consumer(); producer.start(); consumer.start(); } static class Producer extends Thread { public void run() { while (true) { try { System.out.println("老板准备炸油条了，架子上还能放：" + (queueSize - queue.size()) + "根油条"); queue.put("1根油条"); System.out.println("老板炸好了1根油条，架子上还能放：" + (queueSize - queue.size()) + "根油条"); Thread.sleep(produceSpeed); } catch (InterruptedException e) { e.printStackTrace(); } } } } static class Consumer extends Thread { public void run() { while (true) { try { System.out.println("A 准备买油条了，架子上还剩" + queue.size() + "根油条"); queue.take(); System.out.println("A 买到1根油条，架子上还剩" + queue.size() + "根油条"); Thread.sleep(consumeSpeed); System.out.println("B 准备买油条了，架子上还剩" + queue.size() + "根油条"); queue.take(); System.out.println("B 买到1根油条，架子上还剩" + queue.size() + "根油条"); Thread.sleep(consumeSpeed); System.out.println("C 准备买油条了，架子上还剩" + queue.size() + "根油条"); queue.take(); System.out.println("C 买到1根油条，架子上还剩" + queue.size() + "根油条"); Thread.sleep(consumeSpeed); } catch (InterruptedException e) { e.printStackTrace(); } } } }}
ThreadLocal(隔离变量)
/** * Created by fengzp on 16/6/30. */public class ThreadLocalDemo { public static class MyRunnable implements Runnable { private ThreadLocal threadLocal = new ThreadLocal (); @Override public void run() { threadLocal.set((int) (Math.random() * 100D)); System.out.println(Thread.currentThread().getName() + ":" + threadLocal.get()); } } public static void main(String[] args) { Thread t1 = new Thread(new MyRunnable(), "A"); Thread t2 = new Thread(new MyRunnable(), "B"); t1.start(); t2.start(); }} 线程A与线程B中ThreadLocal保存的整型变量是各自独立的，互不相干，只要在每个线程内部使用set方法赋值，然后在线程内部使用get就能取到对应的值。
ThreadLocal还有一个派生的子类：InheritableThreadLocal ，可以允许线程及该线程创建的子线程均可以访问同一个变量(有些OOP中的proteced的意味)
/** * Created by fengzp on 16/6/30. */public class InheritableThreadLocalDemo { private static InheritableThreadLocal threadLocal = new InheritableThreadLocal (); public static class MyRunnable implements Runnable { public MyRunnable(String name) { System.out.println(name + " => " + Thread.currentThread().getName() + ":" + threadLocal.get()); } @Override public void run() { System.out.println(Thread.currentThread().getName() + ":" + threadLocal.get()); } } public static void main(String[] args) { threadLocal.set(1); System.out.println(Thread.currentThread().getName() + ":" + threadLocal.get()); Thread t1 = new Thread(new MyRunnable("R-A"), "A"); Thread t2 = new Thread(new MyRunnable("R-B"), "B"); t1.start(); t2.start(); }}
DaemonThread(守护线程)
在正式理解这个概念前，先把 守护线程 与 守护进程 这二个极其相似的说法区分开，守护进程通常是为了防止某些应用因各种意外原因退出，而在后台独立运行的系统服务或应用程序。 比如：我们开发了一个邮件发送程序，一直不停的监视队列池，发现有待发送的邮件，就将其发送出去。如果这个程序挂了(或被人误操作关了)，邮件就不发出去了，为了防止这种情况，再开发一个类似windows 系统服务的应用，常驻后台，监制这个邮件发送程序是否在运行，如果没运行，则自动将其启动。
而我们今天说的java中的守护线程(Daemon Thread) 指的是一类特殊的Thread，其优先级特别低(低到甚至可以被JVM自动终止)，通常这类线程用于在空闲时做一些资源清理类的工作，比如GC线程，如果JVM中所有非守护线程（即：常规的用户线程）都结束了，守护线程会被JVM中止，想想其实也挺合理，没有任何用户线程了，自然也不会有垃圾对象产生，GC线程也没必要存在了。
public class Program { public static void main(String[] args) { TestThread t1 = new TestThread(); t1.setDaemon(true); t1.start(); } private static class TestThread extends Thread { public void run() { System.out.println("test"); } }} 由于t1设置成Daemon Thread了，运行后，main进程马上就结束，此时没有用户进程在运行，守护进程默认是不执行的，因此运行后，没有任何输出结果，符合我们刚才的解释。
然后再写一个模拟例子，一个常规的用户线程负责写入日志，一个守护线程负责清除日志
/** * Created by fengzp on 16/6/30. */public class DamonThreadDemo { private static int queueCapacity = 10; private static BlockingQueue logQueue = new ArrayBlockingQueue (queueCapacity); public static void main(String[] args) throws IOException { LogWriter writer = new LogWriter(); LogCleaner cleaner = new LogCleaner(); cleaner.setDaemon(true); writer.start(); cleaner.start(); } /** * 模拟不停写日志（直到队列写满） */ private static class LogWriter extends Thread { public void run() { for (int i = 0; i < queueCapacity; i++) { try { logQueue.put("" + i); System.out.println("日志已写入，当前日志内容：" + logQueue); Thread.sleep(500); } catch (InterruptedException e) { e.printStackTrace(); } } } } /** * 模拟在空闲时清理日志（仅保留5条日志） */ private static class LogCleaner extends Thread { public void run() { while (true) { if (logQueue.size() > 5) { try { logQueue.take(); System.out.println("多余日志被清理，当前日志内容：" + logQueue); Thread.sleep(500); } catch (InterruptedException e) { e.printStackTrace(); } } } } }}