Javaのベクトル<E>は、私はおそらく何か間違ったことをやっている明確な理由がない

Question

でブロックされたが、これは何が起こるかであるばかり：

私はそれが呼ばれるのを待つ、それが実行され、呼び出し「ベクトル、リスナーを登録します。 clear（） "はロックします。問題は「pipeMsgEvent」方式で行われ、ここでは、ありませんので、フレンドリーに見える、コード（したい場合は、行「これは重要である」に直接移動）である：

public class JxtaCustomer implements PipeMsgListener { 
    public static final int ANSWER_OK  = 0; 
    public static final int ANSWER_TIMEOUT =-1; 
    public static final int ANSWER_NOT_ASKED =-2; 
    public static final int ANSWER_WORKING =-3; 

    public static final int REQ_SENT   = 0; 
    public static final int REQ_INV_PIPE_ID =-1; 
    public static final int REQ_INV_PIPE_IO =-2; 
    public static final int REQ_INV_GROUP_ID =-3; 

    protected int answer; 

    protected JxtaGenericAdvertisement serviceAdv = null; 
    protected JxtaNode ThePeer = null; 

    JxtaBiDiPipe myBiDiPipe = null; 
    protected Vector<Entry> output = null; 

    public JxtaCustomer(JxtaGenericAdvertisement adv, JxtaNode peer) 
    { 
     ThePeer = peer; 
     serviceAdv = new JxtaGenericAdvertisement((Element)adv.getDocument(new MimeMediaType("text/xml"))); 

     answer = ANSWER_NOT_ASKED; 
     Vector<Entry> output = new Vector<Entry>(); 
    } 

    public void pipeMsgEvent(PipeMsgEvent event) 
    { 
     System.out.println("It Works! Uhuuu"); 
     // We received a message 
     Message message = event.getMessage(); 

     System.out.println("Lets GO! Uhuuu"); 
     Message.ElementIterator elIt = message.getMessageElementsOfNamespace(serviceAdv.getName()); 

     System.out.println("A little bit more"); 
     answer = ANSWER_WORKING; 

     System.out.println("enter"); 

     // This is important: Here I get stuck, "clear" 
     // never appears on the screen 
     output.clear(); 
     System.out.println("clear"); 
     while (elIt.hasNext()) { 
      MessageElement mElem = elIt.next(); 
      System.out.println(mElem.getElementName() + " " + mElem.toString()); 
      output.add(new Entry(mElem.getElementName(), mElem.toString())); 
     } 
     System.out.println("leave"); 

     answer = ANSWER_OK; 
    } 

    public int sendRequest(Vector<Entry> params) 
    { 
     try { 

      // Creating Pipe Advertisement 
      String pipeAdvType = PipeAdvertisement.getAdvertisementType(); 
      PipeAdvertisement pipeAd = (PipeAdvertisement)AdvertisementFactory.newAdvertisement(pipeAdvType); 

      URI pipeURI = new URI(serviceAdv.getPipeID()); 
      pipeAd.setPipeID(IDFactory.fromURI(pipeURI)); 
      pipeAd.setType(PipeService.UnicastType); 
      pipeAd.setName(serviceAdv.getName() + " Service Pipe"); 
      pipeAd.setDescription("Created by " + serviceAdv.getName()); 

      // Creating Group 
      JxtaGroup jxgp = ThePeer.getGroupFromID(serviceAdv.getGroupID()); 
      if (null == jxgp) 
       return REQ_INV_GROUP_ID; 

      PeerGroup group = jxgp.getPeerGroup(); 
      if (null == group) 
       return REQ_INV_GROUP_ID; 

      // This is important: In the JxtaBiDiPipe call I register 
      // the callback, while I have access to the code, I think 
      // the problem is in my code 
      myBiDiPipe = new JxtaBiDiPipe(group, pipeAd, 30000, this); 

      if (myBiDiPipe.isBound()) { 
       Thread.sleep(500); 

       Message myMessage = new Message(); 

       if (0 == params.size()) 
        params.add(new Entry("dummy", "null")); 

       for (int i=0; i<params.size(); i++) { 
        String Key = params.get(i).getKey(); 
        String Value = params.get(i).getValue(); 
        StringMessageElement strMsgElem = new StringMessageElement(Key, Value, null); 
        myMessage.addMessageElement(serviceAdv.getName(), strMsgElem); 
       } 

       myBiDiPipe.sendMessage(myMessage); 

       answer = ANSWER_TIMEOUT; 

       return REQ_SENT; 
      } 
     } catch (URISyntaxException e){ 
      e.printStackTrace(); 

      return REQ_INV_PIPE_ID; 
     } catch (IOException e) { 
      return REQ_INV_PIPE_IO; 
     } catch (Exception e) { 
      e.printStackTrace(); 
     } 

     return REQ_INV_PIPE_IO; 
    } 

    public Vector<Entry> getResponse() 
    { 
     Vector<Entry> results = new Vector<Entry>(); 

     if (ANSWER_OK != answer) 
      return results; 

     // This is important: I always call "getState()" and check its value 
     // before calling this method, so you can say it's guaranteed to be 
     // called after answer = ANSWER_OK, which never happens because of the 
     // lock 
     for (int i=0; i<output.size(); i++) 
      results.add(output.get(i)); 

     return results; 
    } 

    public int getState() 
    { 
     int count = 10; 

     return answer; 
    } 
} 

私はいつもJxtaCustomerなどを作成しますこの：私は「スリープ」、「待機」または私は「同期」の作成を呼び出すコードで（この最後の1は決してありません）どこ

ここ

JxtaCustomer customer = new JxtaCustomer(adv, ThePeer); 
Vector<Entry> params = new Vector<Entry>(); 

params.add(new Entry("key1", "value1")); 
params.add(new Entry("key2", "value2")); 

customer.sendRequest(params); 

while(JxtaCustomer.ANSWER_OK != customer.getState()) { 
    // I was actually using synchronized locks and timed waits 
    // but since I'm stuck there I'm using this nonsense instead 
} 

Vector<Entry> response = customer.getResponse(); 

が

$ grep synchronized $(find . -name "*.java") 

$ grep sleep $(find . -name "*.java") 
./Src/net/ubi/jxta/JxtaCustomer.java:    Thread.sleep(500); 

$ grep wait $(find . -name "*.java") 
./App/ExampleServices/SimpleSigner.java: boolean waiting = false; 
./App/ExampleServices/SimpleSigner.java:  waiting = true; 
./App/ExampleServices/SimpleSigner.java:  return (waiting && JxtaCustomer.ANSWER_OK == customer.getState()); 
./App/ExampleServices/SimpleSigner.java:  if (!waiting) 
./App/ExampleServices/SimpleSigner.java:   waiting = false; 
./App/ExampleServices/SimpleSigner.java:   return "Error: Response not ready, wait more time\n"; 

Answer 1

あなたのコンストラクタは、ローカルに設定されます出力と呼ばれる変数ではなくメンバ変数、あなたはそれが後であなたが呼び出すときに、そう

output = new Vector<Entry>(); 

あるべきとき

Vector<Entry> output = new Vector<Entry>(); 

を持ってoutput.clear()あなたは、スローNULLポインタ例外を取得している理由コードドンの次の行実行されません。

「未使用のローカル変数」のようなコンパイラ警告は、これらの種類の間違いを見つけるのに役立ちます。