Thinking in Java学习笔记 Semaphore控制的资源池

SemaphoreDemo.java

一个资源池Pool，可以由多个线程检出和检入其中的资源，由Semaphore控制同步问题，由数组来记录每个资源的检出/检入状态

CheckoutTask这个线程，启动多个，负责检入检出资源。

资源类Fat，有比较复杂的计算

同时在main()方法中对资源进行了检出和检入操作

package com.test.concurrent;import java.util.ArrayList;import java.util.List;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.Future;import java.util.concurrent.Semaphore;import java.util.concurrent.TimeUnit;public class SemaphoreDemo {static final int SIZE=25;public static void main(String[] args) throws InterruptedException {// TODO Auto-generated method stubfinal Pool<Fat> pool=new Pool(SIZE,Fat.class);ExecutorService exec=Executors.newCachedThreadPool();for(int i=0;i<SIZE;i++){exec.execute(new CheckoutTask(pool));}System.out.println("All checkoutTask created!!!");List<Fat> list=new ArrayList<Fat>();for(int i=0;i<SIZE;i++){Fat f=pool.checkOut();System.out.println(i+" : main() thread check out");f.operation();list.add(f);}Future<?> blocked=exec.submit(new Runnable(){public void run(){try {pool.checkOut();} catch (InterruptedException e) {// TODO Auto-generated catch blockSystem.out.println("Checkout Interrupted!!!!!!!!!!!!");e.printStackTrace();}}});TimeUnit.SECONDS.sleep(2);blocked.cancel(true);System.out.println("-------------Checking in objects in "+list);for(int i=0;i<SIZE;i++){Fat item=list.get(i);pool.checkIn(item);}for(Fat f:list){pool.checkIn(f);exec.shutdown();}}}class Pool<T>{private int size;private Semaphore available;private volatile boolean checkOut[];private List<T> items=new ArrayList<T>();public Pool(int size, Class<T> objectClass){this.size=size;available=new Semaphore(size,true);checkOut=new boolean[size];for(int i=0;i<size;i++){try {items.add(objectClass.newInstance());} catch (InstantiationException | IllegalAccessException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}public T checkOut() throws InterruptedException{available.acquire();return getItem();}public void checkIn(T t){if(releaseItem(t))available.release();}private synchronized T getItem(){for(int i=0;i<size;i++){if(!checkOut[i]){checkOut[i]=true;return (T)items.get(i);}}return null;}private synchronized boolean releaseItem(T item){int index=items.indexOf(item);if(index<0){return false;}if(checkOut[index]){checkOut[index]=false;return true;}return false;}}class Fat{private volatile double d; //prevent optimizationprivate static int counter=0;private final int id=counter++;public Fat(){for(int i=0;i<10000;i++){d+=(Math.PI+Math.E);}}public String toString(){return "Fat id: "+id+"  D:"+d;}public void operation(){System.out.println(this);}}class CheckoutTask<T> implements Runnable{private static int counter=0;private final int id=counter++;Pool<T> pool;public CheckoutTask(Pool<T> pool){this.pool=pool;}@Overridepublic void run(){try {T item=pool.checkOut();System.out.println(this+" check out "+item);TimeUnit.SECONDS.sleep(1);System.out.println(this+" check in "+item);pool.checkIn(item);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}}public String toString(){return "CheckoutTask id:"+id+"   ";}}

输出为：

All checkoutTask created!!!
0 : main() thread check out
CheckoutTask id:9    check out Fat id: 9  D:58598.74482048422
CheckoutTask id:4    check out Fat id: 4  D:58598.74482048422
CheckoutTask id:23    check out Fat id: 24  D:58598.74482048422
CheckoutTask id:19    check out Fat id: 17  D:58598.74482048422
CheckoutTask id:0    check out Fat id: 0  D:58598.74482048422
CheckoutTask id:16    check out Fat id: 16  D:58598.74482048422
CheckoutTask id:20    check out Fat id: 18  D:58598.74482048422
CheckoutTask id:6    check out Fat id: 6  D:58598.74482048422
CheckoutTask id:11    check out Fat id: 11  D:58598.74482048422
CheckoutTask id:8    check out Fat id: 8  D:58598.74482048422
CheckoutTask id:7    check out Fat id: 7  D:58598.74482048422
CheckoutTask id:10    check out Fat id: 10  D:58598.74482048422
CheckoutTask id:21    check out Fat id: 22  D:58598.74482048422
CheckoutTask id:22    check out Fat id: 19  D:58598.74482048422
CheckoutTask id:17    check out Fat id: 21  D:58598.74482048422
CheckoutTask id:1    check out Fat id: 1  D:58598.74482048422
CheckoutTask id:12    check out Fat id: 15  D:58598.74482048422
CheckoutTask id:18    check out Fat id: 20  D:58598.74482048422
CheckoutTask id:13    check out Fat id: 12  D:58598.74482048422
CheckoutTask id:2    check out Fat id: 2  D:58598.74482048422
CheckoutTask id:14    check out Fat id: 13  D:58598.74482048422
CheckoutTask id:15    check out Fat id: 14  D:58598.74482048422
Fat id: 23  D:58598.74482048422
CheckoutTask id:3    check out Fat id: 3  D:58598.74482048422
CheckoutTask id:5    check out Fat id: 5  D:58598.74482048422
CheckoutTask id:9    check in Fat id: 9  D:58598.74482048422
CheckoutTask id:20    check in Fat id: 18  D:58598.74482048422
CheckoutTask id:16    check in Fat id: 16  D:58598.74482048422
CheckoutTask id:0    check in Fat id: 0  D:58598.74482048422
1 : main() thread check out
Fat id: 16  D:58598.74482048422
2 : main() thread check out
Fat id: 0  D:58598.74482048422
3 : main() thread check out
Fat id: 18  D:58598.74482048422
CheckoutTask id:4    check in Fat id: 4  D:58598.74482048422
CheckoutTask id:23    check in Fat id: 24  D:58598.74482048422
4 : main() thread check out
Fat id: 4  D:58598.74482048422
5 : main() thread check out
Fat id: 24  D:58598.74482048422
CheckoutTask id:12    check in Fat id: 15  D:58598.74482048422
CheckoutTask id:8    check in Fat id: 8  D:58598.74482048422
6 : main() thread check out
Fat id: 15  D:58598.74482048422
7 : main() thread check out
Fat id: 8  D:58598.74482048422
CheckoutTask id:19    check in Fat id: 17  D:58598.74482048422
CheckoutTask id:24    check out Fat id: 9  D:58598.74482048422
8 : main() thread check out
Fat id: 17  D:58598.74482048422
CheckoutTask id:17    check in Fat id: 21  D:58598.74482048422
9 : main() thread check out
Fat id: 21  D:58598.74482048422
CheckoutTask id:14    check in Fat id: 13  D:58598.74482048422
10 : main() thread check out
Fat id: 13  D:58598.74482048422
CheckoutTask id:11    check in Fat id: 11  D:58598.74482048422
11 : main() thread check out
Fat id: 11  D:58598.74482048422
CheckoutTask id:6    check in Fat id: 6  D:58598.74482048422
12 : main() thread check out
Fat id: 6  D:58598.74482048422
CheckoutTask id:5    check in Fat id: 5  D:58598.74482048422
13 : main() thread check out
Fat id: 5  D:58598.74482048422
CheckoutTask id:7    check in Fat id: 7  D:58598.74482048422
14 : main() thread check out
Fat id: 7  D:58598.74482048422
CheckoutTask id:10    check in Fat id: 10  D:58598.74482048422
15 : main() thread check out
Fat id: 10  D:58598.74482048422
CheckoutTask id:21    check in Fat id: 22  D:58598.74482048422
16 : main() thread check out
Fat id: 22  D:58598.74482048422
CheckoutTask id:22    check in Fat id: 19  D:58598.74482048422
17 : main() thread check out
Fat id: 19  D:58598.74482048422
CheckoutTask id:1    check in Fat id: 1  D:58598.74482048422
18 : main() thread check out
Fat id: 1  D:58598.74482048422
CheckoutTask id:18    check in Fat id: 20  D:58598.74482048422
19 : main() thread check out
Fat id: 20  D:58598.74482048422
CheckoutTask id:13    check in Fat id: 12  D:58598.74482048422
20 : main() thread check out
Fat id: 12  D:58598.74482048422
CheckoutTask id:2    check in Fat id: 2  D:58598.74482048422
21 : main() thread check out
Fat id: 2  D:58598.74482048422
CheckoutTask id:15    check in Fat id: 14  D:58598.74482048422
22 : main() thread check out
Fat id: 14  D:58598.74482048422
CheckoutTask id:3    check in Fat id: 3  D:58598.74482048422
23 : main() thread check out
Fat id: 3  D:58598.74482048422
CheckoutTask id:24    check in Fat id: 9  D:58598.74482048422
24 : main() thread check out
Fat id: 9  D:58598.74482048422
Checkout Interrupted!!!!!!!!!!!!
-------------Checking in objects in [Fat id: 23  D:58598.74482048422, Fat id: 16  D:58598.74482048422, Fat id: 0  D:58598.74482048422, Fat id: 18  D:58598.74482048422, Fat id: 4  D:58598.74482048422, Fat id: 24  D:58598.74482048422, Fat id: 15  D:58598.74482048422, Fat id: 8  D:58598.74482048422, Fat id: 17  D:58598.74482048422, Fat id: 21  D:58598.74482048422, Fat id: 13  D:58598.74482048422, Fat id: 11  D:58598.74482048422, Fat id: 6  D:58598.74482048422, Fat id: 5  D:58598.74482048422, Fat id: 7  D:58598.74482048422, Fat id: 10  D:58598.74482048422, Fat id: 22  D:58598.74482048422, Fat id: 19  D:58598.74482048422, Fat id: 1  D:58598.74482048422, Fat id: 20  D:58598.74482048422, Fat id: 12  D:58598.74482048422, Fat id: 2  D:58598.74482048422, Fat id: 14  D:58598.74482048422, Fat id: 3  D:58598.74482048422, Fat id: 9  D:58598.74482048422]
java.lang.InterruptedException
at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(Unknown Source)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(Unknown Source)
at java.util.concurrent.Semaphore.acquire(Unknown Source)
at com.test.concurrent.Pool.checkOut(SemaphoreDemo.java:73)
at com.test.concurrent.SemaphoreDemo$1.run(SemaphoreDemo.java:31)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)