001 /*
002 * Created on Nov 1, 2007
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
005 * the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
010 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
011 * specific language governing permissions and limitations under the License.
012 *
013 * Copyright @2007-2011 the original author or authors.
014 */
015 package org.fest.util;
016
017 import java.util.*;
018
019 /**
020 * Filters elements of a collection by their data type.
021 * @param <T> the generic type of the objects returned by the filter.
022 *
023 * @author Yvonne Wang
024 */
025 public class TypeFilter<T> implements CollectionFilter<T> {
026
027 /**
028 * Creates a new <code>{@link TypeFilter}</code>.
029 * @param <T> the generic type of the target type.
030 * @param type the target type for this filter.
031 * @return the created filter.
032 */
033 public static <T> TypeFilter<T> byType(Class<T> type) {
034 return new TypeFilter<T>(type);
035 }
036
037 private final Class<T> type;
038
039 TypeFilter(Class<T> type) {
040 this.type = type;
041 }
042
043 /**
044 * Filters the given collection by the type specified in this filter.
045 * @param target the collection to filter.
046 * @return a list containing the filtered elements.
047 * @throws IllegalArgumentException if the given collection is {@code null}.
048 */
049 @SuppressWarnings("unchecked") public List<T> filter(Collection<?> target) {
050 if (target == null) throw new IllegalArgumentException("The collection to filter should not be null");
051 List<Object> filtered = new ArrayList<Object>();
052 for (Object o : target) {
053 if (o == null) continue;
054 if (type.isAssignableFrom(o.getClass())) filtered.add(o);
055 }
056 return (List<T>) filtered;
057 }
058 }