1 |
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2 | package de.ugoe.cs.quest.eventcore.guimodel;
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3 |
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4 | import java.util.IdentityHashMap;
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5 | import java.util.LinkedList;
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6 | import java.util.List;
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7 |
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8 | /**
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9 | * <p>
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10 | * Skeletal implementation for GUI elements.
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11 | * </p>
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12 | *
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13 | * @version 1.0
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14 | * @author Patrick Harms
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15 | */
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16 | public abstract class AbstractDefaultGUIElement implements IGUIElement {
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17 |
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18 | /**
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19 | * <p>
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20 | * Id for object serialization.
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21 | * </p>
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22 | */
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23 | public static final long serialVersionUID = 1L;
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24 |
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25 | /**
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26 | * <p>
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27 | * The reference to equal GUI element manager (needed to preserve singleton behavior, even
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28 | * though the objects are not singleton).
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29 | * </p>
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30 | */
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31 | private static final EqualGUIElementManager equalGUIElementManager =
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32 | new EqualGUIElementManager();
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33 |
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34 | /**
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35 | * <p>
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36 | * Specification of the GUI element
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37 | * </p>
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38 | */
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39 | private final IGUIElementSpec specification;
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40 |
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41 | /**
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42 | * <p>
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43 | * Reference to the parent element
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44 | * </p>
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45 | */
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46 | private final IGUIElement parent;
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47 |
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48 | /**
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49 | * <p>
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50 | * Constructor. Creates a new AbstractDefaultGUIElement.
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51 | * </p>
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52 | *
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53 | * @param specification
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54 | * specification of the created GUI element
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55 | * @param parent
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56 | * parent of the created GUI element; null means the element is a top-level window
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57 | */
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58 | public AbstractDefaultGUIElement(IGUIElementSpec specification, IGUIElement parent) {
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59 | this.specification = specification;
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60 | this.parent = parent;
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61 | }
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62 |
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63 | /*
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64 | * (non-Javadoc)
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65 | *
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66 | * @see de.ugoe.cs.tasktree.guimodel.GUIElement#getSpecification()
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67 | */
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68 | @Override
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69 | public IGUIElementSpec getSpecification() {
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70 | return specification;
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71 | }
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72 |
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73 | /*
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74 | * (non-Javadoc)
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75 | *
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76 | * @see de.ugoe.cs.quest.eventcore.guimodel.IGUIElement#getParent()
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77 | */
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78 | @Override
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79 | public IGUIElement getParent() {
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80 | return parent;
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81 | }
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82 |
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83 | /*
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84 | * (non-Javadoc)
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85 | *
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86 | * @see de.ugoe.cs.quest.eventcore.guimodel.IGUIElement#addEqualGUIElement(IGUIElement)
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87 | */
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88 | @Override
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89 | public void addEqualGUIElement(IGUIElement equalElement) {
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90 | equalGUIElementManager.addEqualGUIElements(this, equalElement);
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91 | }
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92 |
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93 | /*
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94 | * (non-Javadoc)
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95 | *
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96 | * @see GUIElement#equals(GUIElement)
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97 | */
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98 | public final boolean equals(Object other) {
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99 | // implement final, as GUI elements are all singletons and they equal only if they are the
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100 | // same object or if they are in the list of equal GUI elements
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101 | return super.equals(other) || equalGUIElementManager.equals(this, other);
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102 | }
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103 |
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104 | /*
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105 | * (non-Javadoc)
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106 | *
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107 | * @see java.lang.Object#hashCode()
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108 | */
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109 | @Override
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110 | public final int hashCode() {
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111 | // implement final, as GUI elements are all singletons and they equal only if they are the
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112 | // same object. If there are several GUI element objects that represent the same GUI element
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113 | // then they are stored in the list of equal elements. In this case, the hash code of the
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114 | // list is unique within the system
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115 | return equalGUIElementManager.hashCode(this);
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116 | }
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117 |
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118 | /**
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119 | * <p>
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120 | * This internal helper class manages equal GUI elements. This is necessary, as we often first
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121 | * identify many GUI elements as different and later use a heuristic to determine that they are
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122 | * the same. This class provides the means to preserve the singleton behavior of the GUI
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123 | * elements after we merge two GUI elements.
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124 | * </p>
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125 | *
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126 | * @version 1.0
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127 | * @author Patrick Harms
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128 | */
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129 | private static class EqualGUIElementManager {
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130 |
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131 | /**
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132 | * <p>
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133 | * The internal map of GUI elements mapping each registered element to its equal variants.
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134 | * We use the {@link IdentityHashMap} as a normal hash map would not work because of the
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135 | * changing of the hash code of GUI elements at runtime.
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136 | * </p>
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137 | */
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138 | private IdentityHashMap<IGUIElement, List<IGUIElement>> identityHashMap =
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139 | new IdentityHashMap<IGUIElement, List<IGUIElement>>();
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140 |
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141 | /**
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142 | * <p>
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143 | * Adds a new equals relationship between two {@link IGUIElement}s to the equality manager.
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144 | * </p>
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145 | *
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146 | * @param guiElement1
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147 | * first equal GUI element
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148 | * @param guiElement2
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149 | * second equal GUI element
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150 | */
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151 | private synchronized void addEqualGUIElements(IGUIElement guiElement1,
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152 | IGUIElement guiElement2)
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153 | {
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154 | List<IGUIElement> list1 = identityHashMap.get(guiElement1);
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155 | List<IGUIElement> list2 = identityHashMap.get(guiElement2);
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156 |
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157 | if (list1 == null) {
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158 | if (list2 == null) {
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159 | list2 = new LinkedList<IGUIElement>();
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160 | list2.add(guiElement1);
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161 | list2.add(guiElement2);
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162 | identityHashMap.put(guiElement1, list2);
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163 | identityHashMap.put(guiElement2, list2);
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164 | }
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165 | else {
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166 | addIfNotContained(list2, guiElement1);
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167 | identityHashMap.put(guiElement1, list2);
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168 | }
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169 | }
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170 | else {
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171 | if (list2 == null) {
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172 | addIfNotContained(list1, guiElement2);
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173 | identityHashMap.put(guiElement2, list1);
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174 | }
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175 | else if (list1 != list2) {
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176 | list1.addAll(list2);
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177 | identityHashMap.put(guiElement2, list1);
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178 | }
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179 | // else
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180 | // in this case, both GUI elements should already be registered with the same
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181 | // lists.
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182 | }
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183 | }
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184 |
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185 | /**
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186 | * <p>
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187 | * Returns the object hash of a {@link IGUIElement}.
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188 | * </p>
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189 | *
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190 | * @param guiElement
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191 | * gui element whose object hash is determined
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192 | * @return the object hash
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193 | */
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194 | private synchronized int hashCode(IGUIElement guiElement) {
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195 | return System.identityHashCode(getEqualElementsList(guiElement));
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196 | }
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197 |
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198 | /**
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199 | * <p>
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200 | * Determines the equality of two {@link IGUIElement}s based on the information of the
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201 | * identify manager. Two elements are equal, if they have been added as equal using
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202 | * {@link #addEqualGUIElements(IGUIElement, IGUIElement)}.
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203 | * </p>
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204 | *
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205 | * @param guiElement
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206 | * GUI element to which the object is compared
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207 | * @param other
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208 | * object that is compared to the GUI element
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209 | * @return
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210 | */
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211 | private synchronized boolean equals(IGUIElement guiElement, Object other) {
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212 | if (other instanceof IGUIElement) {
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213 | for (IGUIElement candidate : getEqualElementsList(guiElement)) {
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214 | if (candidate == other) {
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215 | return true;
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216 | }
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217 | }
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218 | }
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219 |
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220 | return false;
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221 | }
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222 |
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223 | /**
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224 | * <p>
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225 | * Returns the equal {@link IGUIElement} of a given {@link IGUIElement}.
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226 | * </p>
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227 | *
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228 | * @param guiElement
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229 | * GUI element of which the equal elements are returned
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230 | * @return the equal GUI elements
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231 | */
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232 | private List<IGUIElement> getEqualElementsList(IGUIElement guiElement) {
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233 | List<IGUIElement> returnValue = identityHashMap.get(guiElement);
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234 |
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235 | if (returnValue == null) {
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236 | returnValue = new LinkedList<IGUIElement>();
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237 | returnValue.add(guiElement);
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238 | identityHashMap.put(guiElement, returnValue);
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239 | }
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240 |
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241 | return returnValue;
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242 | }
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243 |
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244 | /**
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245 | * <p>
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246 | * Adds {@link IGUIElement} as equal to a list of {@link IGUIElement} if and only if it is
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247 | * not already contained.
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248 | * </p>
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249 | *
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250 | * @param equalElementsList
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251 | * list of {@link IGUIElement} to which the GUI element is added
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252 | * @param guiElement
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253 | * GUI element to be added
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254 | */
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255 | private void addIfNotContained(List<IGUIElement> equalElementsList, IGUIElement guiElement)
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256 | {
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257 | for (IGUIElement candidate : equalElementsList) {
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258 | if (candidate == guiElement) {
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259 | return;
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260 | }
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261 | }
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262 |
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263 | equalElementsList.add(guiElement);
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264 | }
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265 |
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266 | }
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267 |
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268 | }
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