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 005 * in compliance with 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 010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 011 * or implied. See the License for the specific language governing permissions and limitations under 012 * the License. 013 * 014 * Copyright @2007 the original author or authors. 015 */ 016 package org.fest.util; 017 018 import java.util.ArrayList; 019 import java.util.Collection; 020 import java.util.List; 021 022 /** 023 * Understands filtering elements of a collection by their data type. 024 * @param <T> the generic type of the objects returned by the filter. 025 * 026 * @author Yvonne Wang 027 */ 028 public class TypeFilter<T> implements CollectionFilter<T> { 029 030 /** 031 * Creates a new <code>{@link TypeFilter}</code>. 032 * @param <T> the generic type of the target type. 033 * @param type the target type for this filter. 034 * @return the created filter. 035 */ 036 public static <T> TypeFilter<T> byType(Class<T> type) { 037 return new TypeFilter<T>(type); 038 } 039 040 private final Class<T> type; 041 042 TypeFilter(Class<T> type) { 043 this.type = type; 044 } 045 046 /** 047 * Filters the given collection by the type specified in this filter. 048 * @param target the collection to filter. 049 * @return a list containing the filtered elements. 050 * @throws IllegalArgumentException if the given collection is <code>null</code>. 051 */ 052 @SuppressWarnings("unchecked") 053 public List<T> filter(Collection<?> target) { 054 if (target == null) throw new IllegalArgumentException("The collection to filter should not be null"); 055 List<Object> filtered = new ArrayList<Object>(); 056 for (Object o : target) { 057 if (o == null) continue; 058 if (type.isAssignableFrom(o.getClass())) filtered.add(o); 059 } 060 return (List<T>)filtered; 061 } 062 }