Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2006 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/ package org.eclipse.ui.internal.ide.dialogs; import org.eclipse.core.resources.IContainer; import org.eclipse.core.resources.IResource; import org.eclipse.jface.viewers.Viewer; import org.eclipse.jface.viewers.ViewerComparator; /** * Sorter for viewers that display items of type <code>IResource</code>. * The sorter supports two sort criteria: * <p> * <code>NAME</code>: Folders are given order precedence, followed by files. * Within these two groups resources are ordered by name. All name comparisons * are case-insensitive. * </p> * <p> * <code>TYPE</code>: Folders are given order precedence, followed by files. * Within these two groups resources are ordered by extension. All extension * comparisons are case-insensitive. * </p> * <p> * This class may be instantiated; it is not intended to be subclassed. * </p> */ public class ResourceComparator extends ViewerComparator { /** * Constructor argument value that indicates to sort items by name. */ public final static int NAME = 1; /** * Constructor argument value that indicates to sort items by extension. */ public final static int TYPE = 2; private int criteria; /** * Creates a resource sorter that will use the given sort criteria. * * @param criteria the sort criterion to use: one of <code>NAME</code> or * <code>TYPE</code> */ public ResourceComparator(int criteria) { super(); this.criteria = criteria; } /** * Returns an integer value representing the relative sort priority of the * given element based on its class. * <p> * <ul> * <li>resources (<code>IResource</code>) - 2</li> * <li>project references (<code>ProjectReference</code>) - 1</li> * <li>everything else - 0</li> * </ul> * </p> * * @param element the element * @return the sort priority (larger numbers means more important) */ protected int classComparison(Object element) { if (element instanceof IResource) { return 2; } return 0; } /* (non-Javadoc) * Method declared on ViewerSorter. */ public int compare(Viewer viewer, Object o1, Object o2) { //have to deal with non-resources in navigator //if one or both objects are not resources, returned a comparison //based on class. if (!(o1 instanceof IResource && o2 instanceof IResource)) { return compareClass(o1, o2); } IResource r1 = (IResource) o1; IResource r2 = (IResource) o2; if (r1 instanceof IContainer && r2 instanceof IContainer) { return compareNames(r1, r2); } else if (r1 instanceof IContainer) { return -1; } else if (r2 instanceof IContainer) { return 1; } else if (criteria == NAME) { return compareNames(r1, r2); } else if (criteria == TYPE) { return compareTypes(r1, r2); } else { return 0; } } /** * Returns a number reflecting the collation order of the given elements * based on their class. * * @param element1 the first element to be ordered * @param element2 the second element to be ordered * @return a negative number if the first element is less than the * second element; the value <code>0</code> if the first element is * equal to the second element; and a positive number if the first * element is greater than the second element */ protected int compareClass(Object element1, Object element2) { return classComparison(element1) - classComparison(element2); } /** * Returns a number reflecting the collation order of the given resources * based on their resource names. * * @param resource1 the first resource element to be ordered * @param resource2 the second resource element to be ordered * @return a negative number if the first element is less than the * second element; the value <code>0</code> if the first element is * equal to the second element; and a positive number if the first * element is greater than the second element */ protected int compareNames(IResource resource1, IResource resource2) { return getComparator().compare(resource1.getName(), resource2.getName()); } /** * Returns a number reflecting the collation order of the given resources * based on their respective file extensions. Resources with the same file * extension will be collated based on their names. * * @param resource1 the first resource element to be ordered * @param resource2 the second resource element to be ordered * @return a negative number if the first element is less than the * second element; the value <code>0</code> if the first element is * equal to the second element; and a positive number if the first * element is greater than the second element */ protected int compareTypes(IResource resource1, IResource resource2) { String ext1 = getExtensionFor(resource1); String ext2 = getExtensionFor(resource2); // Compare extensions. If they're different then return a value that // indicates correct extension ordering. If they're the same then // return a value that indicates the correct NAME ordering. int result = getComparator().compare(ext1, ext2); if (result != 0) { return result; } return compareNames(resource1, resource2); } /** * Returns the sort criteria of this this sorter. * * @return the sort criterion: one of <code>NAME</code> or <code>TYPE</code> */ public int getCriteria() { return criteria; } /** * Returns the extension portion of the given resource. * * @param resource the resource * @return the file extension, possibily the empty string */ private String getExtensionFor(IResource resource) { String ext = resource.getFileExtension(); return ext == null ? "" : ext; //$NON-NLS-1$ } }