Check whether the given Collection contains the given element instance.
import java.util.Arrays; import java.util.Collection; import java.util.Enumeration; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.Properties; /* * Copyright 2002-2007 the original author or authors. * * 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. *//** * Miscellaneous collection utility methods. * Mainly for internal use within the framework. * * @author Juergen Hoeller * @author Rob Harrop * @since 1.1.3 */abstractclass CollectionUtils { /** * Check whether the given Collection contains the given element instance. * <p>Enforces the given instance to be present, rather than returning * <code>true</code> for an equal element as well. * @param collection the Collection to check * @param element the element to look for * @return <code>true</code> if found, <code>false</code> else */publicstaticboolean containsInstance(Collection collection, Object element) { if (collection != null) { for (Iterator it = collection.iterator(); it.hasNext();) { Object candidate = it.next(); if (candidate == element) { return true; } } } return false; } /** * Return <code>true</code> if the supplied Collection is <code>null</code> * or empty. Otherwise, return <code>false</code>. * @param collection the Collection to check * @return whether the given Collection is empty */publicstaticboolean isEmpty(Collection collection) { return (collection == null || collection.isEmpty()); } /** * Return <code>true</code> if the supplied Map is <code>null</code> * or empty. Otherwise, return <code>false</code>. * @param map the Map to check * @return whether the given Map is empty */publicstaticboolean isEmpty(Map map) { return (map == null || map.isEmpty()); } /** * Return <code>true</code> if any element in '<code>candidates</code>' is * contained in '<code>source</code>'; otherwise returns <code>false</code>. * @param source the source Collection * @param candidates the candidates to search for * @return whether any of the candidates has been found */publicstaticboolean containsAny(Collection source, Collection candidates) { if (isEmpty(source) || isEmpty(candidates)) { return false; } for (Iterator it = candidates.iterator(); it.hasNext();) { if (source.contains(it.next())) { return true; } } return false; } /** * Return the first element in '<code>candidates</code>' that is contained in * '<code>source</code>'. If no element in '<code>candidates</code>' is present in * '<code>source</code>' returns <code>null</code>. Iteration order is * {@link Collection} implementation specific. * @param source the source Collection * @param candidates the candidates to search for * @return the first present object, or <code>null</code> if not found */publicstatic Object findFirstMatch(Collection source, Collection candidates) { if (isEmpty(source) || isEmpty(candidates)) { return null; } for (Iterator it = candidates.iterator(); it.hasNext();) { Object candidate = it.next(); if (source.contains(candidate)) { return candidate; } } return null; } /** * Find a value of the given type in the given Collection. * @param collection the Collection to search * @param type the type to look for * @return a value of the given type found, or <code>null</code> if none * @throws IllegalArgumentException if more than one value of the given type found */publicstatic Object findValueOfType(Collection collection, Class type) throws IllegalArgumentException { if (isEmpty(collection)) { return null; } Class typeToUse = (type != null ? type : Object.class); Object value = null; for (Iterator it = collection.iterator(); it.hasNext();) { Object obj = it.next(); if (typeToUse.isInstance(obj)) { if (value != null) { thrownew IllegalArgumentException("More than one value of type [" + typeToUse.getName() + "] found"); } value = obj; } } return value; } /** * Determine whether the given Collection only contains a single unique object. * @param collection the Collection to check * @return <code>true</code> if the collection contains a single reference or * multiple references to the same instance, <code>false</code> else */publicstaticboolean hasUniqueObject(Collection collection) { if (isEmpty(collection)) { return false; } boolean hasCandidate = false; Object candidate = null; for (Iterator it = collection.iterator(); it.hasNext();) { Object elem = it.next(); if (!hasCandidate) { hasCandidate = true; candidate = elem; } elseif (candidate != elem) { return false; } } return true; } } Related examples in the same category
