执行器服务 invokeAll

Question

我对可调用接口还很陌生。我有一些代码目前无法编译，只是需要一些帮助来解释为什么....

public List<String> getNonPingableRegisters (Collection<RegisterReplicationSynchTime> nonReplicatingRegisters) throws IOException {

    int nThreads = 15;
    final ExecutorService es = Executors.newFixedThreadPool(nThreads);

    Collection<Callable<PingTask>> pingTasks = new ArrayList<Callable<PingTask>>(nonReplicatingRegisters.size());
    for (RegisterReplicationSynchTime nonReplicatingRegister : nonReplicatingRegisters) {
        pingTasks.add(new PingTask(nonReplicatingRegister.getRegisterName()));
    }

    List<Future<String>> taskResults = es.invokeAll(pingTasks);
    List<String> results = new ArrayList<String>();

    for (Future<String> taskResult : taskResults) {
        try {
            String output = taskResult.get();
            if (StringUtils.isNotEmpty(output) ) {
                results.add(output);
            }
        } catch (InterruptedException e) {
            // handle accordingly
        } catch (ExecutionException e) {
            // handle accordingly          
        }
    }
    return results;
}

PingTask 在哪里...

public class PingTask implements Callable<String> {

    private String hostname = null;

    public PingTask(String hostname) {
        this.hostname = hostname;
    }

        public String call() {
            Socket socket = null;
            boolean reachable = false;  
            try {                           
                socket = new Socket();
                socket.connect(new InetSocketAddress(hostname, 139), 1000); //1 sec timeout                     
                reachable = true;
                socket.close();
            } catch (IOException e) {

            }
            finally {
                if (socket != null) {
                    try {
                        socket.close();
                    } catch (IOException e) {

                    }
                }
            }       
            return (reachable ? "" : hostname);
        }

    }

编译错误在...

List<Future<String>> taskResults = es.invokeAll(pingTasks);

类型 Collection> 中的方法 add(Callable) 不适用于参数 (PingTask) StoreReplicationSynchtimeManagerImpl.java

不确定我需要在这里做什么来调用 invokeAll。非常感谢您的帮助。

谢谢

Answer 1

这是你的错误：

Collection<Callable<PingTask>> pingTasks = new ArrayList<Callable<PingTask>>(nonReplicatingRegisters.size());

PingTask 实现 Callable<String>，而不是 Callable<PingTask>。您需要将列表声明为 Collection<PingTask> 或 Collection<Callable<String>>.

Answer 2

错误不在该行。它位于：

pingTasks.add(new PingTask(nonReplicatingRegister.getRegisterName()));

您的集合是 Callable，而您的 PingTask class 实现了 Callable。将集合更改为：

Collection<Callable<String>>

Answer 3

类型不匹配。

 Collection<Callable<PingTask>> pingTasks = new ArrayList<Callable<PingTask>>

但是 PingTask 声明为

public class PingTask implements Callable<String>

将集合更改为 Collection<PingTask>

pingTasks.add(new PingTask(nonReplicatingRegister.getRegisterName()));

会由于Callable<String>类型添加而导致编译时错误

执行器服务 invokeAll

Executor Service invokeAll

java

multithreading

executorservice