Question

我正在使用Java 1.5从命令行读取多个参数。参数是平面文件的名称。我通过main方法中的参数循环并调用一个方法，该方法又创建了一堆线程来处理文件。我需要暂停循环，直到处理完第一个参数的所有线程完成，然后继续为第二个参数创建线程。如何在我的main方法中对参数进行排队或暂停循环执行，直到所有线程处理当前参数完成？

Answer 1

使用Threadpool和Executor。看一下java.util.concurrent包。

for(String argument:args){
  //you said you want multiple threads to work on a single argument.
  //create callables instead and use a ThreadPool
  List<Callable<YourResult>> lstCallables = createCallablesFor(argument);
  List<Future<YourResult>> futures = Executors.newCachedThreadPool().invokeAll(lstCallables);
  for(Future<YourResult> future:futures){
    //this get() waits until the thread behind the current future is done.
    // it also returns whatever your callable might return.
    future.get(); 
  }
  // at this point, all the threads working on the current argument are finished
  // and the next loop iteration works on the next argument
}

Answer 2

我想知道你是否在寻找像cyclic barriers这样的东西。

Answer 3

您需要在循环内启动一个参数的线程作业，以便在完成一个作业后，启动下一个循环并启动下一个参数的下一个线程作业。此外，您可以在您定义它的线程作业中工作。

示例：这只是一个片段

for (int i = 0; i < count; i++) {
    t[i] = new RunDemo();
    String[] serverList = srv[i].split(",");
    String logName = filename + "_" + serverList[0] + "_log";
    String sql = "INSERT INTO .....(any query)";
    t[i].setStr("sqlplus -L " + username[i] + "/" + password[i] + "@"
                + serverList[1] + ":" + serverList[2] + "/" + serverList[3]
                + " @" + filename1);
    t[i].setLogName(logName);
    t[i].setDirectory(dir);
    try{
        conn.UpdateQuery(sql);
        log.info("Inserted into the table data with query " + sql);
    }
    catch (Exception e){
        log.info("The data can't be inserted into table with " + e.getMessage() + " sql query " + sql);
    }
    new Thread(t[i]).start();
}

这里在每个循环中创建并启动具有不同serverList的新线程。

现在，作业定义如下：

public void run() {
    JShell jshell = new JShell();
    try {
        log.info("Command is: " + this.str + " log name: " + this.LogName + " in directory: " + this.directory);
        jshell.executeCommand(this.str, this.LogName, this.directory);
        log.info("Executed command successfully");
    } catch (Exception e1) {
        log.info("Error at executing command with error stack: ");
        e1.printStackTrace();
    }
    DBConnection conn1 = new DBConnection();
    String sql = "UPDATE patcheventlog SET ENDTIME=SYSDATE WHERE LOGFILE='" + this.directory + this.LogName + "'";
    try {
        //conn1.callConnection("192.168.8.81", "d2he");

        conn1.callConnection(ip, sid);

        conn1.UpdateQuery(sql);
        conn1.disposeConnection();
    } catch (SQLException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
    System.out.print(this.LogName);
}

所以这就是你如何使用循环内的线程。你不需要暂停你的循环。

希望有所帮助。

在main方法中暂停执行循环，直到所有Threads完成Java 1.5

3 个答案: