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1 /*******************************************************************************
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2 * Copyright (c) 2007, 2008 IBM Corporation and others.
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3 * All rights reserved. This program and the accompanying materials
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4 * are made available under the terms of the Eclipse Public License v1.0
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5 * which accompanies this distribution, and is available at
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6 * http://www.eclipse.org/legal/epl-v10.html
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7 *
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8 * Contributors:
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9 * IBM Corporation - initial API and implementation
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10 *******************************************************************************/
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11 module org.eclipse.core.internal.databinding.Queue;
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12
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13 import java.lang.all;
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14
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15 /**
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16 * Created to avoid a dependency on java.util.LinkedList, see bug 205224.
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17 *
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18 * @since 1.1
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19 *
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20 */
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21 public class Queue {
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22
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23 static class Entry {
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24 Object object;
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25
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26 this(Object o) {
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27 this.object = o;
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28 }
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29
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30 Entry next;
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31 }
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32
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33 Entry first;
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34 Entry last;
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35
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36 /**
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37 * Adds the given object to the end of the queue.
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38 *
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39 * @param o
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40 */
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41 public void enqueue(Object o) {
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42 Entry oldLast = last;
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43 last = new Entry(o);
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44 if (oldLast !is null) {
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45 oldLast.next = last;
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46 } else {
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47 first = last;
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48 }
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49 }
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50
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51 /**
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52 * Returns the first object in the queue. The queue must not be empty.
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53 *
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54 * @return the first object
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55 */
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56 public Object dequeue() {
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57 Entry oldFirst = first;
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58 if (oldFirst is null) {
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59 throw new IllegalStateException();
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60 }
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61 first = oldFirst.next;
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62 if (first is null) {
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63 last = null;
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64 }
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65 oldFirst.next = null;
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66 return oldFirst.object;
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67 }
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68
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69 /**
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70 * Returns <code>true</code> if the list is empty.
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71 *
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72 * @return <code>true</code> if the list is empty
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73 */
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74 public bool isEmpty() {
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75 return first is null;
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76 }
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77 }
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