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 }