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1 package treeVnc;
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2
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3 import java.util.concurrent.CountDownLatch;
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4
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5 public class MulticastQueue<T>
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6 {
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7
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8 Node<T> tail;
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9
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10 public MulticastQueue()
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11 {
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12 tail = new Node<T>(null);
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13 }
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14
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15 public synchronized void put(T item)
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16 {
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17 Node<T> next = new Node<T>(item);
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18 tail.set(next);
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19 tail = next;
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20 }
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21
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22 public Client<T> newClient()
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23 {
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24 return new Client<T>(tail);
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25 }
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26
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27 static class Client<T>
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28 {
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29 Node<T> node;
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30
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31 Client(Node<T> tail)
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32 {
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33 node = tail;
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34 }
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35
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36 synchronized public T poll()
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37 {
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38 Node<T> next = null;
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39 T item = null;
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40 do {
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41 try {
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42 next = node.next();
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43 }catch(InterruptedException _e){
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44 continue;
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45 }
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46 // item = node.getItem();
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47 item = next.getItem();
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48 node = next;
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49 } while ( item == null);
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50 return item;
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51 }
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52 }
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53
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54 static class Node<T>
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55 {
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56 private T item;
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57 private Node<T> next;
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58 private CountDownLatch latch;
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59
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60 public Node(T item)
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61 {
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62 this.item = item;
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63 this.next = null;
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64 latch = new CountDownLatch(1);
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65 }
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66
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67 synchronized public T getItem() {
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68 return item;
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69 }
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70
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71 public void set(Node<T> next)
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72 {
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73 this.next = next;
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74 latch.countDown();
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75 }
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76
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77 public Node<T> next() throws InterruptedException
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78 {
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79 latch.await();
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80 return next;
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81 }
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82
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83 synchronized public void clear() {
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84 item = null;
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85 }
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86 }
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87 }
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