java线程池实例

  1 package thread.pool2;
  2 
  3 import java.util.LinkedList;
  4 
  5 public class ThreadPool {
  6     //最大线程数
  7     private int maxCapacity;
  8     //初始线程数
  9     private int initCapacity;
 10     //当前线程数
 11     private int currentCapacity;
 12     //线程池需要执行的任务
 13     private LinkedList<Task> tasks;
 14     //当前处于等待的线程数
 15     private int waitThreadNum = 0;
 16     //线程池中线程数超过初始数量时，此时有线程执行完任务,但是没有后续的任务执行,则会等待一段时间后，该线程才销毁
 17     //destroyTime小于或等于0时,线程立即消费,大于0,则等待设置的时间
 18     private int destroyTime = 0;
 19     
 20     public ThreadPool(int initCapacity,int maxCapacity, int destroyTime) {
 21         if(initCapacity > maxCapacity) {
 22             //初始线程数不能超过最大线程数,当然此处可以抛出异常,提示不允许这么设置
 23             initCapacity = maxCapacity;
 24         }
 25         this.maxCapacity = maxCapacity;
 26         this.initCapacity = initCapacity;
 27         this.currentCapacity = initCapacity;
 28         this.tasks = new LinkedList<Task>();
 29         this.waitThreadNum = initCapacity;
 30         this.destroyTime = destroyTime;
 31     }
 32     /**
 33      * 向线程池中添加任务,如果线程数不够,则增加线程数,但线程数总量不能超过给定的最大线程数
 34      * @param task
 35      */
 36     public synchronized void addTask(Task task) {
 37         tasks.add(task);
 38         addThread();
 39         notifyAll();
 40     }
 41     /**
 42      * 从线程池中取出任务,如果没有任务,则当前线程处于等待状态
 43      * @return
 44      * @throws InterruptedException
 45      */
 46     public synchronized Task getTask() throws InterruptedException {
 47         while(tasks.isEmpty()) {
 48             wait();
 49         }
 50         //取出第一个任务的同时将第一个任务移除
 51         return tasks.pollFirst();
 52     }
 53     /**
 54      * 判断线程池中任务列表是否为空
 55      * @return
 56      */
 57     public synchronized boolean isEmpty() {
 58         return tasks.isEmpty();
 59     }
 60     /**
 61      * 活跃线程数加1
 62      */
 63     public synchronized void addWaitThreadNum(int num) {
 64         waitThreadNum += num;
 65     }
 66     /**
 67      * 活跃线程数减1
 68      */
 69     public synchronized void reduceWaitThreadNum(int num) {
 70         waitThreadNum -= num;
 71     }
 72     
 73     /**
 74      * 启动线程池
 75      */
 76     public void execute() {
 77         System.out.println(initCapacity);
 78         for(int i = 0; i < initCapacity; i++) {
 79             (new Thread(new InnerThread(this, "thread"+ i))).start();
 80         }
 81     }
 82     /**
 83      * 如果当前线程数大于初始线程数,则关闭当前线程,否则当前线程处于等待状态
 84      * @return
 85      * @throws InterruptedException 
 86      */
 87     public synchronized boolean waitOrClose(int tmp) throws InterruptedException {
 88         System.out.println(currentCapacity + ":" + initCapacity);
 89         //线程退出前,等待一段时间,防止线程频繁创建和销毁线程
 90         if(destroyTime > 0) {
 91             wait(destroyTime);
 92         }
 93         if(currentCapacity > initCapacity && tasks.isEmpty()) {
 94             currentCapacity--;
 95             System.out.println("任务执行完后,当前线程数：" + currentCapacity);
 96             return false;
 97         }
 98         System.out.println("线程等待结束");
 99         addWaitThreadNum(tmp);
100         wait();
101         return true;
102     }
103     
104     /**
105      * 当线程池内线程数不够时,如果有任务在等待处理,同时当前线程都处于非等待状态,
106      * 则增加线程池中线程数,但不能超过线程池中最大线程数
107      */
108     public synchronized void addThread() {
109         System.out.println("当前线程数：" + currentCapacity + "最大线程数：" + maxCapacity + "等待线程数" + waitThreadNum);
110         if(currentCapacity < maxCapacity && waitThreadNum == 0) {
111             //每添加一个线程,当前线程数加1
112             currentCapacity++;
113             //每添加一个线程,相当于线程池中多了一个等待的线程
114             waitThreadNum++;
115             System.out.println("当前线程数为：" + currentCapacity);
116             new Thread(new InnerThread(this, "thread" + (currentCapacity-1))).start();
117         }
118     }
119     /**
120      * 线程池中单个线程对象
121      * @author yj
122      *
123      */
124     private class InnerThread implements Runnable {
125         
126         private ThreadPool threadPool;
127         private String threadName;
128         
129         public InnerThread(ThreadPool threadPool, String threadName) {
130             this.threadPool = threadPool;
131             this.threadName = threadName;
132         }
133 
134         @Override
135         public void run() {
136             try {
137                 while(true){
138                     int addWait = 0;
139                     int resuceWait = 1;
140                     //不等于空,则处理任务
141                     while(!threadPool.isEmpty()) {
142                         threadName = Thread.currentThread().getName();
143                         reduceWaitThreadNum(resuceWait);
144                         Task task = threadPool.getTask();
145                         task.execute(threadName);
146                         try {
147                             Thread.sleep(9000);
148                         } catch (InterruptedException e) {
149                             e.printStackTrace();
150                         }
151                         System.out.println(threadName + "对"+task.getTaskName()+"+任务进行了处理");
152                         //只有处理任务后回到等待状态的线程才将waitThreadNum加1
153                         addWait = 1;
154                         //如果不跳出循环,则等待线程数不减少
155                         resuceWait = 0;
156                     }
157                     //等于空,则等待任务或关闭当前线程
158                     if(threadPool.waitOrClose(addWait)) {    
159                         System.out.println(threadName + "处于等待状态");
160                         continue;
161                     }
162                     //关闭线程
163                     break;
164                 }                
165             } catch (InterruptedException e) {
166                 e.printStackTrace();
167             }
168         }
169     }
170 }