ifclosure.java

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/*
 *  Copyright 2001-2004,2006 The Apache Software Foundation
 *
 *  Licensed 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.collections.functors;

import java.io.Serializable;

import org.apache.commons.collections.Closure;
import org.apache.commons.collections.Predicate;

/**
 * Closure implementation acts as an if statement calling one or other closure
 * based on a predicate.
 * 
 * @since Commons Collections 3.0
 * @version $Revision: 375766 $ $Date: 2006-02-07 23:10:36 +0000 (Tue, 07 Feb 2006) $
 *
 * @author Stephen Colebourne
 * @author Matt Benson
 */
public class IfClosure implements Closure, Serializable {

    /** Serial version UID */
    private static final long serialVersionUID = 3518477308466486130L;

    /** The test */
    private final Predicate iPredicate;
    /** The closure to use if true */
    private final Closure iTrueClosure;
    /** The closure to use if false */
    private final Closure iFalseClosure;

    /**
     * Factory method that performs validation.
     * <p>
     * This factory creates a closure that performs no action when
     * the predicate is false.
     * 
     * @param predicate  predicate to switch on
     * @param trueClosure  closure used if true
     * @return the <code>if</code> closure
     * @throws IllegalArgumentException if either argument is null
     * @since Commons Collections 3.2
     */
    public static Closure getInstance(Predicate predicate, Closure trueClosure) {
        return getInstance(predicate, trueClosure, NOPClosure.INSTANCE);
    }

    /**
     * Factory method that performs validation.
     * 
     * @param predicate  predicate to switch on
     * @param trueClosure  closure used if true
     * @param falseClosure  closure used if false
     * @return the <code>if</code> closure
     * @throws IllegalArgumentException if any argument is null
     */
    public static Closure getInstance(Predicate predicate, Closure trueClosure, Closure falseClosure) {
        if (predicate == null) {
            throw new IllegalArgumentException("Predicate must not be null");
        }
        if (trueClosure == null || falseClosure == null) {
            throw new IllegalArgumentException("Closures must not be null");
        }
        return new IfClosure(predicate, trueClosure, falseClosure);
    }

    /**
     * Constructor that performs no validation.
     * Use <code>getInstance</code> if you want that.
     * <p>
     * This constructor creates a closure that performs no action when
     * the predicate is false.
     * 
     * @param predicate  predicate to switch on, not null
     * @param trueClosure  closure used if true, not null
     * @since Commons Collections 3.2
     */
    public IfClosure(Predicate predicate, Closure trueClosure) {
        this(predicate, trueClosure, NOPClosure.INSTANCE);
    }

    /**
     * Constructor that performs no validation.
     * Use <code>getInstance</code> if you want that.
     * 
     * @param predicate  predicate to switch on, not null
     * @param trueClosure  closure used if true, not null
     * @param falseClosure  closure used if false, not null
     */
    public IfClosure(Predicate predicate, Closure trueClosure, Closure falseClosure) {
        super();
        iPredicate = predicate;
        iTrueClosure = trueClosure;
        iFalseClosure = falseClosure;
    }

    /**
     * Executes the true or false closure accoring to the result of the predicate.
     * 
     * @param input  the input object
     */
    public void execute(Object input) {
        if (iPredicate.evaluate(input) == true) {
            iTrueClosure.execute(input);
        } else {
            iFalseClosure.execute(input);
        }
    }

    /**
     * Gets the predicate.
     * 
     * @return the predicate
     * @since Commons Collections 3.1
     */
    public Predicate getPredicate() {
        return iPredicate;
    }

    /**
     * Gets the closure called when true.
     * 
     * @return the closure
     * @since Commons Collections 3.1
     */
    public Closure getTrueClosure() {
        return iTrueClosure;
    }

    /**
     * Gets the closure called when false.
     * 
     * @return the closure
     * @since Commons Collections 3.1
     */
    public Closure getFalseClosure() {
        return iFalseClosure;
    }

}