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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
package org.apache.commons.collections4.functors;
import java.io.Serializable;
import org.apache.commons.collections4.Predicate;
import org.apache.commons.collections4.Transformer;
/**
* Transformer implementation that will call one of two closures based on whether a predicate evaluates
* as true or false.
*
* @param The input type for the transformer
* @param The output type for the transformer
*
* @since 4.1
*/
public class IfTransformer implements Transformer, Serializable {
/** Serial version UID */
private static final long serialVersionUID = 8069309411242014252L;
/** The test */
private final Predicate iPredicate;
/** The transformer to use if true */
private final Transformer iTrueTransformer;
/** The transformer to use if false */
private final Transformer iFalseTransformer;
/**
* Factory method that performs validation.
*
* @param input type for the transformer
* @param output type for the transformer
* @param predicate predicate to switch on
* @param trueTransformer transformer used if true
* @param falseTransformer transformer used if false
* @return the if transformer
* @throws NullPointerException if either argument is null
*/
public static Transformer ifTransformer(final Predicate predicate,
final Transformer trueTransformer,
final Transformer falseTransformer) {
if (predicate == null) {
throw new NullPointerException("Predicate must not be null");
}
if (trueTransformer == null || falseTransformer == null) {
throw new NullPointerException("Transformers must not be null");
}
return new IfTransformer<>(predicate, trueTransformer, falseTransformer);
}
/**
* Factory method that performs validation.
*
* This factory creates a transformer that just returns the input object when
* the predicate is false.
*
* @param input and output type for the transformer
* @param predicate predicate to switch on
* @param trueTransformer transformer used if true
* @return the if transformer
* @throws NullPointerException if either argument is null
*/
public static Transformer ifTransformer(
final Predicate predicate,
final Transformer trueTransformer) {
if (predicate == null) {
throw new NullPointerException("Predicate must not be null");
}
if (trueTransformer == null) {
throw new NullPointerException("Transformer must not be null");
}
return new IfTransformer<>(predicate, trueTransformer, NOPTransformer.nopTransformer());
}
/**
* Constructor that performs no validation.
* Use the static factory method ifTransformer if you want that.
*
* @param predicate predicate to switch on, not null
* @param trueTransformer transformer used if true, not null
* @param falseTransformer transformer used if false, not null
*/
public IfTransformer(final Predicate predicate,
final Transformer trueTransformer,
final Transformer falseTransformer) {
super();
iPredicate = predicate;
iTrueTransformer = trueTransformer;
iFalseTransformer = falseTransformer;
}
/**
* Transforms the input using the true or false transformer based to the result of the predicate.
*
* @param input the input object to transform
* @return the transformed result
*/
@Override
public O transform(final I input) {
if(iPredicate.evaluate(input)){
return iTrueTransformer.transform(input);
}
return iFalseTransformer.transform(input);
}
/**
* Gets the predicate.
*
* @return the predicate
*/
public Predicate getPredicate(){
return iPredicate;
}
/**
* Gets the transformer used when true.
*
* @return the transformer
*/
public Transformer getTrueTransformer() {
return iTrueTransformer;
}
/**
* Gets the transformer used when false.
*
* @return the transformer
*/
public Transformer getFalseTransformer() {
return iFalseTransformer;
}
}