001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.collections4.functors; 018 019import java.io.Serializable; 020import java.util.Objects; 021 022import org.apache.commons.collections4.FunctorException; 023import org.apache.commons.collections4.Predicate; 024import org.apache.commons.collections4.Transformer; 025 026/** 027 * Predicate implementation that returns the result of a transformer. 028 * 029 * @since 3.0 030 */ 031public final class TransformerPredicate<T> implements Predicate<T>, Serializable { 032 033 /** Serial version UID */ 034 private static final long serialVersionUID = -2407966402920578741L; 035 036 /** 037 * Factory to create the predicate. 038 * 039 * @param <T> the type that the predicate queries 040 * @param transformer the transformer to decorate 041 * @return the predicate 042 * @throws NullPointerException if the transformer is null 043 */ 044 public static <T> Predicate<T> transformerPredicate(final Transformer<? super T, Boolean> transformer) { 045 return new TransformerPredicate<>(Objects.requireNonNull(transformer, "transformer")); 046 } 047 048 /** The transformer to call */ 049 private final Transformer<? super T, Boolean> iTransformer; 050 051 /** 052 * Constructor that performs no validation. 053 * Use {@code transformerPredicate} if you want that. 054 * 055 * @param transformer the transformer to decorate 056 */ 057 public TransformerPredicate(final Transformer<? super T, Boolean> transformer) { 058 iTransformer = transformer; 059 } 060 061 /** 062 * Evaluates the predicate returning the result of the decorated transformer. 063 * 064 * @param object the input object 065 * @return true if decorated transformer returns Boolean.TRUE 066 * @throws FunctorException if the transformer returns an invalid type 067 */ 068 @Override 069 public boolean evaluate(final T object) { 070 final Boolean result = iTransformer.transform(object); 071 if (result == null) { 072 throw new FunctorException( 073 "Transformer must return an instanceof Boolean, it was a null object"); 074 } 075 return result.booleanValue(); 076 } 077 078 /** 079 * Gets the transformer. 080 * 081 * @return the transformer 082 * @since 3.1 083 */ 084 public Transformer<? super T, Boolean> getTransformer() { 085 return iTransformer; 086 } 087 088}