java - 如何停止悬吊线程池中的多个线程执行同一条语句？

Question

如何防止吊索线程池中的线程执行以下语句:serv.getService()。start(tic，info);
如果执行已由一个线程完成多次？

我尝试使用_alreadyExecuted标志，但这似乎无济于事。

日志:/image/x8jZw.png

我的代码如下，

     private void sendBlock( service serv, String tic, Resource block, 
     Update update, Info info, ResourceResolver resolver ) throws 
     IOException {
     private Boolean _alreadyExecuted = Boolean.FALSE;
     if( tic != null ) {
        String tic = null;
        if(!_alreadyExecuted){
             getLogger().info("Before startSubmission. Currently _alreadyexecuted is " +_alreadyExecuted);
             serv.getService().start( tic, info );
             getLogger().info("After startSubmission, _alreadyexecuted is about to change to true. Currently _alreadyexecuted is " +_alreadyExecuted);
             _alreadyExecuted = Boolean.TRUE;
             getLogger().info("After startSubmission, _alreadyexecuted has been changed to true. Currently _alreadyexecuted is " +_alreadyExecuted);
        }
    }
}

Answer 1

将字段更改为volatile:

 private volatile Boolean _alreadyExecuted = Boolean.FALSE;

在多线程执行环境中，允许线程缓存字段的值(通常这样做)。关键字 volatile确保所有线程使用分配给该字段的当前(相同)值。