接收的參數不一樣
submit有返回值，而execute沒有
Method submit extends base method Executor.execute by creating and returning a Future that can be used to cancel execution and/or wait for completion.
3、submit方便Exception處理
There is a difference when looking at exception handling. If your tasks throws an exception and if it was submitted with execute this exception will go to the uncaught exception handler (when you don't have provided one explicitly, the default one will just print the stack trace to System.err). If you submitted the task with submit any thrown exception, checked or not, is then part of the task's return status. For a task that was submitted with submit and that terminates with an exception, the Future.get will rethrow this exception, wrapped in an ExecutionException.
submit()能在返回的Future對象調用get()方法的時候再次拋出線程中的異常，而execute()會交由線程的UncaughtExceptionHandler去處理。