Question

如何确保第一次迭代由One Thread运行，第二次迭代由Another Thread运行。

在下面的代码片段中，runQuery方法执行Query并将resultSet作为输出。

我有两个这样的查询，我想在Parallel中同时运行。

for (int i = 0; i < list.size(); i++) {
    String ProcessedRecord = list.get(i);
    String app_name = application.get(i);

    // ResultSet feedDetails = runQuery(ProcessedRecord,app_name); 
    try {
        System.out.println("Inside try block ... ");
        ResultSet feedDetails = dat.runQuery(ProcessedRecord, app_name);
        rs_feedDetails.add(feedDetails); 
    } catch(SQLException e) {
        e.printStackTrace();
    }
}

Answer 1

您可以在ExecutorService，Callables和Futures的帮助下完成此操作。

以下是修改后的代码：

    ExecutorService pool = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors()); //A thread pool to execute your tasks
    List<Future<ResultSet>> futures = new ArrayList<>(); //List to hold futures

    for (int i = 0; i < list.size(); i++) {
        String ProcessedRecord = list.get(i);
        String app_name = application.get(i);

        // ResultSet feedDetails = runQuery(ProcessedRecord,app_name); 
        try {
            Future<ResultSet> toAdd = pool.submit(new Callable<ResultSet>() { //submit a callable of resultset to the pool
                @Override
                public ResultSet call() throws Exception {
                    return dat.runQuery(ProcessedRecord, app_name);
                }
            });
            futures.add(toAdd);
        } catch(SQLException e) {
            e.printStackTrace();
        }
    }
    pool.shutdown(); // shut down the thread pool
    for(int i = 0; i < futures.size(); i++) {
        rs_feedDetails.add(futures.get(i).get()); //invoke get method of every future in your list. The get method will return you the result.
    }

修改

正如评论中所提到的，在某些情况下，任务可以在同一个线程上串行执行 - 可以使用ExecutorService参数强制并行，例如“parallelism”或“amountThreads”

如何使用Threads并行运行两个查询

1 个答案: