Java tutorial
/** * Copyright (C) 2012 JBoss Inc * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.jboss.dashboard.commons.comparator; import org.apache.commons.collections.CollectionUtils; import java.util.*; /** * Helper class containing methods for the comparison between different types. */ public class ComparatorUtils { /** * Compares two comparable objects. * * @param ordering: 1=ascending, -1=descending */ public static int compare(Comparable o1, Comparable o2, int ordering) { // Compare int comp = 0; if (o1 == null && o2 != null) comp = -1; else if (o1 != null && o2 == null) comp = 1; else if (o1 == null && o2 == null) comp = 0; else { comp = o1.compareTo(o2); if (comp > 0) comp = 1; else if (comp < 0) comp = -1; } // Resolve ordering if (ordering == -1) return comp * ordering; return comp; } /** * Compares two dates. * * @param ordering: 1=ascending, -1=descending */ public static int compare(Date o1, Date o2, int ordering) { // Compare int comp = 0; if (o1 == null && o2 != null) comp = -1; else if (o1 != null && o2 == null) comp = 1; else if (o1 == null && o2 == null) comp = 0; else { long thisTime = o1.getTime(); long anotherTime = o2.getTime(); comp = (thisTime < anotherTime ? -1 : (thisTime == anotherTime ? 0 : 1)); } // Resolve ordering if (ordering == -1) return comp * ordering; return comp; } /** * Compares two booleans. * * @param ordering: 1=ascending, -1=descending */ public static int compare(Boolean o1, Boolean o2, int ordering) { // Compare int comp = 0; if (o1 == null && o2 != null) comp = -1; else if (o1 != null && o2 == null) comp = 1; else if (o1 == null && o2 == null) comp = 0; else { if (o1.booleanValue() == o2.booleanValue()) comp = 0; else if (o1.booleanValue()) comp = 1; else comp = -1; } // Resolve ordering if (ordering == -1) return comp * ordering; return comp; } /** * Check if tow collections contains exactly the same elements. * The order of elements within each collection is not relevant. */ public static boolean equals(Collection o1, Collection o2) { if (o1 == null && o2 != null) return false; else if (o1 != null && o2 == null) return false; else if (o1 == null && o2 == null) return false; else if (o1.size() != o2.size()) return false; else if (o1.isEmpty() && o2.isEmpty()) return false; else return CollectionUtils.intersection(o1, o2).size() == o1.size(); } /** * Compares two collections. * A collection is considered greater than other if it has one element greater than all other collection elements. * * @param ordering: 1=ascending, -1=descending */ public static int compare(Collection o1, Collection o2, int ordering) { // Compare int comp = 0; if (o1 == null && o2 != null) comp = -1; else if (o1 != null && o2 == null) comp = 1; else if (o1 == null && o2 == null) comp = 0; else if (o1.size() == 0 && o2.size() > 0) comp = -1; else if (o1.size() > 0 && o2.size() == 0) comp = 1; else { // Compare o1 elements vs o2 int o1comp = 0; Iterator it = o1.iterator(); while (it.hasNext()) { Object value = it.next(); o1comp = compare(value, o2, ordering); if (o1comp != 0) { if (o1comp == -1) comp = -1; if (o1comp == 1 && comp != -1) comp = 1; // -1 is prioritary. } } // Compare o2 elements vs o1 int o2comp = 0; it = o2.iterator(); while (comp == 0 && it.hasNext()) { Object value = it.next(); o2comp = compare(value, o1, ordering); if (o2comp != 0) { if (o2comp == -1) comp = 1; if (o2comp == 1 && comp != -1) comp = -1; // -1 is prioritary. } } } // Resolve ordering if (ordering == -1) return comp * ordering; return comp; } /** * Compare an element with the collection elements. * The element is greater than the collection if it is greater than ALL of its elements. * The element is smaller than the collection if it is smaller than ALL of its elements. * * @param ordering: 1=ascending, -1=descending */ public static int compare(Object obj, Collection col, int ordering) { // Compare int comp = 0; if (obj == null && col == null) comp = 0; else if (obj == null && col != null && col.size() > 0) comp = -1; else if (obj != null && (col == null || col.size() == 0)) comp = 1; else { // Both collections have the same size. Iterator it = col.iterator(); while (it.hasNext()) { Object value = it.next(); comp += compare(obj, value, ordering); } // Check comparison hits. if (comp == col.size()) comp = 1; else if (comp == (col.size() * -1)) comp = -1; else comp = 0; } // Resolve ordering if (ordering == -1) return comp * ordering; return comp; } /** * Compares two objects. * Only Object satisfying the following nterfaces can be compared: Comparable, Boolean and Collection. * * @param ordering: 1=ascending, -1=descending */ public static int compare(Object o1, Object o2, int ordering) { // Compare int comp = 0; if (o1 == null && o2 != null) comp = -1; else if (o1 != null && o2 == null) comp = 1; else if (o1 == null && o2 == null) comp = 0; else { if (o1 instanceof Boolean && o2 instanceof Boolean) { return ComparatorUtils.compare((Boolean) o1, (Boolean) o2, ordering); } if (o1 instanceof Date && o2 instanceof Date) { return ComparatorUtils.compare((Date) o1, (Date) o2, ordering); } else if (o1 instanceof Collection && o2 instanceof Collection) { return ComparatorUtils.compare((Collection) o1, (Collection) o2, ordering); } else if (o1 instanceof Comparable && o2 instanceof Comparable) { return ComparatorUtils.compare((Comparable) o1, (Comparable) o2, ordering); } } // Resolve ordering if (ordering == -1) return comp * ordering; return comp; } /** * Test compare methods. */ public static void main(String[] args) throws Exception { String[] stringArray = new String[] { "3", "4", "1" }; Long[] longArray = new Long[] { new Long(3), new Long(2), new Long(4) }; Boolean[] booleanArray = new Boolean[] { Boolean.FALSE, Boolean.TRUE, Boolean.FALSE }; List stringList = Arrays.asList(stringArray); List longList = Arrays.asList(longArray); List booleanList = Arrays.asList(booleanArray); List collection1 = Arrays.asList(new String[] { "A" }); List collection2 = Arrays.asList(new String[] { "B" }); Comparator comparator = new Comparator() { public int compare(Object o1, Object o2) { return ComparatorUtils.compare(o1, o2, -1); } }; Collections.sort(stringList, comparator); Collections.sort(longList, comparator); Collections.sort(booleanList, comparator); System.out.println(stringList); System.out.println(longList); System.out.println(booleanList); System.out.println(comparator.compare(collection1, collection2)); } }