并行计算框架的Java实现--系列三

优化锁，之前的锁是采用一个static的Object实现的，这要就会有一个问题，如果我创建了多个Executer，那么所有Job都会持有一把锁，既影响性能，也容易出现死锁的情况。所以，改成每个Executer持有一把锁。
Executer代码如下：

Java代码
public class Executer {
    //计算已经派发的任务数(条件谓词)
    public static int THREAD_COUNT = 0;
    //存储任务的执行结果
    private List<Future<Object>> futres = new ArrayList<Future<Object>>();
    //条件队列锁
    public final Object lock = new Object();
    //线程池
    private ExecutorService pool = null;
    public Executer() {
        this(1);
    }
    public Executer(int threadPoolSize) {
        pool = Executors.newFixedThreadPool(threadPoolSize);
    }
    /**
     * 任务派发
     * @param job
     */
    public void fork(Job job){
        //设置同步锁
        job.setLock(lock);
        //将任务派发给线程池去执行
        futres.add(pool.submit(job));
        //增加线程数
        synchronized (lock) {
            THREAD_COUNT++;
        }
    }
    /**
     * 统计任务结果
     */
    public List<Object> join(){
        synchronized (lock) {
            while(THREAD_COUNT > 0){//检查线程数，如果为0，则表示所有任务处理完成
                System.out.println("threadCount: "+THREAD_COUNT);
                try {
                    lock.wait();//如果任务没有全部完成，则挂起。等待完成的任务给予通知
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
        List<Object> list = new ArrayList<Object>();
        //取出每个任务的处理结果，汇总后返回
        for (Future<Object> future : futres) {
            try {
                Object result = future.get();//因为任务都已经完成，这里直接get
                list.add(result);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return list;
    }
}
Job类:

Java代码
public abstract class Job implements Callable<Object> {

    //锁
    private Object lock = null;

    void setLock(Object lock) {
        this.lock = lock;
    }

    @Override
    public Object call() throws Exception {
        Object result = this.execute();//执行子类具体任务
        synchronized (lock) {
            //处理完业务后，任务结束，递减线程数，同时唤醒主线程
            Executer.THREAD_COUNT--;
            lock.notifyAll();
        }
        return result;
    }
    /**
     * 业务处理函数
     */
    public abstract Object execute();

}
测试结果：

Java代码
threadCount: 10
running thread id = 8
running thread id = 10
running thread id = 9
running thread id = 12
running thread id = 11
threadCount: 8
threadCount: 7
threadCount: 6
threadCount: 5
running thread id = 12
running thread id = 8
running thread id = 11
threadCount: 2
running thread id = 10
threadCount: 1
running thread id = 9
ResultSize: 10
time: 2001

补充：软件开发 , Java ,