java.util.concurrent包的拆解

java.util.concurrent包：
1.locks部分：顯式鎖（互斥鎖和速寫鎖）相關
2.atomic部分：原子變量類相關，是構建非阻塞算法的基礎
3.executor部分：線程池相關
4.collection部分：并發容器相關
5.tools部分：同步工具相關，如信號量、閉鎖、柵欄等功能

1.collection部分:
1.1 BlockingQueue
BlockingQueue為接口，如果要用它，需要實現它的子類：
ArrayBlockingQueue
DelayQueue
LinkedBlockingQueue
SynchronousQueue
PriorityBlockingQueue
TransferQueue

   /**

• 在兩個獨立的線程中啟動一個Producer和一個Consumer
• Producer向一個共享的BlockingQueue注入字符串，而Comsumer從中拿出來
• @Author mufeng

• @Date 2019-7-8 11:25
  */
  public class BlockingQueueExample {
  public static void main(String[] args) {
  BlockingQueue blockingQueue=new ArrayBlockingQueue(1024);
  Producer producer=new Producer(blockingQueue);
  Consumer consumer=new Consumer(blockingQueue);
  new Thread(producer).start();
  new Thread(consumer).start();
  try {
  Thread.sleep(4000);
  } catch (InterruptedException e) {
  e.printStackTrace();
  }
  }
  }
  class Producer implements Runnable{
  private BlockingQueue blockingQueue;
  public Producer(BlockingQueue blockingQueue){this.blockingQueue=blockingQueue;
  }
  @Override
  br/>this.blockingQueue=blockingQueue;
  }
  @Override
  try {
  blockingQueue.put("1");
  Thread.sleep(1000);
  blockingQueue.put("2");
  Thread.sleep(1000);
  blockingQueue.put("3");
  Thread.sleep(1000);
  } catch (InterruptedException e) {
  e.printStackTrace();
  }
  }
  }
  class Consumer implements Runnable{
  private BlockingQueue blockingQueue;
  public Consumer(BlockingQueue blockingQueue){
  this.blockingQueue=blockingQueue;
  }

  @Override
  public void run() {
  try {
  System.out.println(blockingQueue.take());
  System.out.println(blockingQueue.take());
  System.out.println(blockingQueue.take());
  } catch (InterruptedException e) {
  e.printStackTrace();
  }
  }
  }

2.Tools部分
2.1 CountDownLatch用法

/**

• @Author mufeng
• @Date 2019-7-8 11:54
  */
  public class TestCountDownLatch {
  public static void main(String[] args) {
  final CountDownLatch countDownLatch=new CountDownLatch(2);
  new Thread(){
  public void run(){
  System.out.println(Thread.currentThread().getName()+"processing");
  try {
  Thread.sleep(3000);
  System.out.println(Thread.currentThread().getName()+"ended");
  countDownLatch.countDown();
  } catch (InterruptedException e) {
  e.printStackTrace();
  }
  }
  }.start();
  new Thread(){
  public void run(){
  System.out.println(Thread.currentThread().getName()+"processing");
  try {
  Thread.sleep(3000);
  System.out.println(Thread.currentThread().getName()+"ended");
  countDownLatch.countDown();
  } catch (InterruptedException e) {
  e.printStackTrace();
  }
  }
  }.start();
  try {
  System.out.println("wait success...");
  countDownLatch.await();//調用await（）方法的線程會被掛起，會等待直到count值為0才繼續執行
  System.out.println("2 end");
  } catch (Exception e) {
  e.printStackTrace();
  }
  }
  }

/**

• 所有線程都停留在柵欄的位置，都結束，才繼續執行
• @Author mufeng
• @Date 2019-7-8 14:10
  */
  public class TestCyclicBarrier {
  public static void main(String[] args) {
  int n=4;
  CyclicBarrier cyclicBarrier=new CyclicBarrier(n);
  for(int i=0;i<n;i++)
  new Writer(cyclicBarrier).start();
  }

}
class Writer extends Thread{
private CyclicBarrier cyclicBarrier;
public Writer(CyclicBarrier cyclicBarrier){
this.cyclicBarrier=cyclicBarrier;
}
public void run(){
try {
System.out.println("writer start");
Thread.sleep(5000);
System.out.println("writer end");
cyclicBarrier.await();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (BrokenBarrierException e) {
e.printStackTrace();
}
System.out.println("continue...");
}
}

/**

• Semaphore可以控制同時訪問的線程個數，通過acquire()獲取一個許可，如果沒有就等待，而release()釋放一個許可。
• @Author mufeng
• @Date 2019-7-8 14:32
  */
  public class TestSemaphore {
  public static void main(String[] args) {
  int N=8;//工人數
  Semaphore semaphore=new Semaphore(5);//機器數
  for(int i=0;i<N;i++){
  new Worker(i,semaphore).start();
  }
  }
  }
  class Worker extends Thread{
  private int num;
  private Semaphore semaphore;
  public Worker(int num,Semaphore semaphore){
  this.num=num;
  this.semaphore=semaphore;
  }
  public void run(){
  try {
  semaphore.acquire();
  System.out.println("工人"+this.num+"occupy a machine。。。");
  Thread.sleep(2000);
  semaphore.release();
  System.out.println("工人"+this.num+"release a machine");
  } catch (InterruptedException e) {
  e.printStackTrace();
  }
  }
  }

/**

• Exchanger是在兩個任務之間交換對象的柵欄，當這些任務進入柵欄時，它們各自擁有一個對象，當它們離開時，它們都擁有之前由對象持有的對象
• @Author mufeng
• @Date 2019-7-8 14:54
  */
  public class TestExchanger {
  public static void main(String[] args) {
  ExecutorService executor =Executors.newCachedThreadPool();
  final Exchanger exchanger=new Exchanger();
  executor.execute(new Runnable() {@Override
  br/>@Override
  String data1="li";
  doExchangeWork(data1,exchanger);
  }
  });
  executor.execute(new Runnable() {@Override
  br/>@Override
  String data1="zhang";
  doExchangeWork(data1,exchanger);
  }
  });
  executor.shutdown();
  }
  private static void doExchangeWork(String data1,Exchanger exchanger){
  System.out.println(Thread.currentThread().getName()+"exchange:"+data1);
  try {
  String data2 = (String) exchanger.exchange(data1);
  System.out.println(Thread.currentThread().getName()+"exchange to"+data2);
  } catch (InterruptedException e) {
  e.printStackTrace();
  }
  }
  }

3.Executor
四種線程池：newFixedThreadPool,newCachedThreadPool,newSingleThreadExecutor,newScheduledThreadPool
1.newFixedThreadPool創建一個可重用固定線程數的線程池，以共享的×××隊列方式來運行線程。
2.newCachedThreadPool創建一個可緩存線程池，如果線程池長度超過處理需要，可靈活回收空閑線程
3.newScheduledThreadPool創建一個定長線程池，支持定時及周期性任務執行
4.newSingleThreadExecutor創建一個單線程化的線程池，它只會用唯一的工作線程來執行任務，保證所有任務按照指定順序（FIFO,LIFO,優先級)執行

任務分兩類：一類是實現了Runnable接口的類，一類是實現了Callable接口的類， Callable的call（）方法只能通過ExecutorService的submit(Callable task)方法來執行，
并且返回一個Future.

4.lock
Synchronized缺點
1.無法中斷
2.無法設置超時
3.使用在方法上的synchronized其實是個語法糖

lock(),trylock(),tryLock(long time,TimeUnit unit)和lockInterruptibly()是用來獲取鎖的，unlock（）方法是用來釋放鎖的。

ReentrantLock 可重入鎖

5.atomic
標量類：AtomicBoolean,AtomicInteger,AtomicLong,AtomicReference
數組類：AtomicIntegerArray,AtomicLongArray,AtomicReferenceArray
更新器類：AtomicLongFieldUpdater,AtomicIntegerFieldUpdater,AtomicReferenceFieldUpdater
復合變量類：AtomicMarkableReference,AtomicStampedReference