Java多线程无法正常工作

Question

I am using an Executor with 4 threads.

Executor exec = Executors.newFixedThreadPool(this.numOfThreads);
        Runnable requestHandler = new Runnable() {
            @Override
            public void run() {
                try {
                    getImageForURL(spURL, 0);
                } catch (IOException ex) {
                } catch (Exception ex) {
                }
            }
        };
        exec.execute(requestHandler);

In getImageForURL , I am printing the name of the thread and the output looks like this. The output does not look right, or is this how it is suppose to look?

name=pool-1-thread-1
name=pool-2-thread-1
name=pool-3-thread-1
name=pool-4-thread-1
name=pool-5-thread-1
name=pool-6-thread-1
name=pool-7-thread-1
name=pool-8-thread-1
name=pool-9-thread-1
name=pool-10-thread-1
name=pool-11-thread-1
name=pool-12-thread-1
name=pool-13-thread-1
name=pool-14-thread-1

Answer 1

You are creating a new pool every time (by repeatedly calling newFixedThreadPool ). You probably want to create the pool just once (when you start your program), and submit multiple requestHandler to it.

The output should then look something like:

name=pool-1-thread-1
name=pool-1-thread-1
name=pool-1-thread-2
name=pool-1-thread-1
name=pool-1-thread-1
name=pool-1-thread-2

with the thread number going up to 4 if the pool is fully utilized.

Answer 2

You want your loop to surround just the call to exec.execute(requestHandler) , and not the entire block of code that you have there, otherwise you'll be creating a new threadpool every time.

If you loop around just the call to exec.execute(requestHandler) , then your output should look something like this (the order of the statements may vary):

pool-1-thread-1
pool-1-thread-4
pool-1-thread-3
pool-1-thread-2
pool-1-thread-3
pool-1-thread-4
pool-1-thread-1
pool-1-thread-4
pool-1-thread-3