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:
- 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:
- 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:
- 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
OK!
这样每个Executer就可以使用自己的lock,而相互不受同步的影响
posted on 2012-07-15 01:21
mixer-a 阅读(1097)
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