What is the difference between ExecutorService.submit and ExecutorService.execute in this code in Java?

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你的背包
你的背包 2021-01-30 00:05

I am learning to use ExectorService to pool threads and send out tasks. I have a simple program below

import java.util.concurrent.Execu         


        
8条回答
  •  Happy的楠姐
    2021-01-30 00:48

    basically both calls execute,if u want future object you shall call submit() method here from the doc

    public  Future submit(Callable task) {
        if (task == null) throw new NullPointerException();
        RunnableFuture ftask = newTaskFor(task);
        execute(ftask);
        return ftask;
    }
    
    
    public  Future submit(Runnable task, T result) {
        if (task == null) throw new NullPointerException();
        RunnableFuture ftask = newTaskFor(task, result);
        execute(ftask);
        return ftask;
    }
    

    as you can see java really has no way to start a thread other than calling run() method, IMO. since i also found that Callable.call() method is called inside run() method. hence if the object is callable it would still call run() method, which inturn would call call() method from doc.

    public void run() {
        if (state != NEW ||
            !UNSAFE.compareAndSwapObject(this, runnerOffset,
                                         null, Thread.currentThread()))
            return;
        try {
            Callable c = callable;
            if (c != null && state == NEW) {
                V result;
                boolean ran;
                try {
                    result = c.call();
                    ran = true;
                } catch (Throwable ex) {
                    result = null;
                    ran = false;
                    setException(ex);
                }
                if (ran)
                    set(result);
            }
        } finally {
            // runner must be non-null until state is settled to
            // prevent concurrent calls to run()
            runner = null;
            // state must be re-read after nulling runner to prevent
            // leaked interrupts
            int s = state;
            if (s >= INTERRUPTING)
                handlePossibleCancellationInterrupt(s);
        }
    }
    

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