如何使用单个Spark上下文在Apache Spark中运行并发作业（动作）

尝试这样的事情：

    final JavaSparkContext sc = new JavaSparkContext("local[2]","Simple_App");    ExecutorService executorService = Executors.newFixedThreadPool(2);    // Start thread 1    Future<Long> future1 = executorService.submit(new Callable<Long>() {        @Override        public Long call() throws Exception { JavaRDD<String> file1 = sc.textFile("/path/to/test_doc1"); return file1.count();        }    });    // Start thread 2    Future<Long> future2 = executorService.submit(new Callable<Long>() {        @Override        public Long call() throws Exception { JavaRDD<String> file2 = sc.textFile("/path/to/test_doc2"); return file2.count();        }    });    // Wait thread 1    System.out.println("File1:"+future1.get());    // Wait thread 2    System.out.println("File2:"+future2.get());