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1 /*******************************************************************************
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2 * Copyright (c) 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.jface.databinding.viewers.TreeStructureAdvisor;
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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 * Instances of this class can be used to improve accuracy and performance of an
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17 * {@link ObservableListTreeContentProvider} or an
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18 * {@link ObservableSetTreeContentProvider}. This class is intended to be
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19 * subclassed by clients.
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20 *
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21 * @since 1.2
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22 *
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23 */
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24 public abstract class TreeStructureAdvisor {
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25
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26 /**
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27 * Returns the parent for the given element, or <code>null</code>
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28 * indicating that the parent can't be computed. In this case the
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29 * tree-structured viewer can't expand a given node correctly if requested.
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30 * The default implementation returns null; clients should override.
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31 *
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32 * @param element
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33 * the element
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34 * @return the parent element, or <code>null</code> if it has none or if
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35 * the parent cannot be computed
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36 */
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37 public Object getParent(Object element) {
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38 return null;
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39 }
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40
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41 /**
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42 * Returns whether the given element has children, or <code>null</code> if
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43 * the actual children collection should be consulted. The default
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44 * implementation returns null; clients should override.
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45 * <p>
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46 * Intended as an optimization for when the viewer does not need the actual
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47 * children. Clients may be able to implement this more efficiently than
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48 * <code>getChildren</code>.
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49 * </p>
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50 *
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51 * @param element
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52 * the element
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53 * @return <code>Boolean.TRUE</code> if the given element has children,
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54 * <code>Boolean.FALSE</code> if it has no children, or
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55 * <code>null</code> if the children collection should be
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56 * consulted.
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57 */
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58 public Boolean hasChildren(Object element) {
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59 return null;
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60 }
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61
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62 }
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