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;
020
021import org.apache.commons.collections4.Closure;
022import org.apache.commons.collections4.Predicate;
023
024/**
025 * Closure implementation that executes a closure repeatedly until a condition is met,
026 * like a do-while or while loop.
027 *
028 * @since 3.0
029 * @version $Id: WhileClosure.html 972421 2015-11-14 20:00:04Z tn $
030 */
031public class WhileClosure<E> implements Closure<E>, Serializable {
032
033    /** Serial version UID */
034    private static final long serialVersionUID = -3110538116913760108L;
035
036    /** The test condition */
037    private final Predicate<? super E> iPredicate;
038    /** The closure to call */
039    private final Closure<? super E> iClosure;
040    /** The flag, true is a do loop, false is a while */
041    private final boolean iDoLoop;
042
043    /**
044     * Factory method that performs validation.
045     *
046     * @param <E> the type that the closure acts on
047     * @param predicate  the predicate used to evaluate when the loop terminates, not null
048     * @param closure  the closure the execute, not null
049     * @param doLoop  true to act as a do-while loop, always executing the closure once
050     * @return the <code>while</code> closure
051     * @throws IllegalArgumentException if the predicate or closure is null
052     */
053    public static <E> Closure<E> whileClosure(final Predicate<? super E> predicate,
054                                              final Closure<? super E> closure, final boolean doLoop) {
055        if (predicate == null) {
056            throw new IllegalArgumentException("Predicate must not be null");
057        }
058        if (closure == null) {
059            throw new IllegalArgumentException("Closure must not be null");
060        }
061        return new WhileClosure<E>(predicate, closure, doLoop);
062    }
063
064    /**
065     * Constructor that performs no validation.
066     * Use <code>whileClosure</code> if you want that.
067     *
068     * @param predicate  the predicate used to evaluate when the loop terminates, not null
069     * @param closure  the closure the execute, not null
070     * @param doLoop  true to act as a do-while loop, always executing the closure once
071     */
072    public WhileClosure(final Predicate<? super E> predicate, final Closure<? super E> closure, final boolean doLoop) {
073        super();
074        iPredicate = predicate;
075        iClosure = closure;
076        iDoLoop = doLoop;
077    }
078
079    /**
080     * Executes the closure until the predicate is false.
081     *
082     * @param input  the input object
083     */
084    public void execute(final E input) {
085        if (iDoLoop) {
086            iClosure.execute(input);
087        }
088        while (iPredicate.evaluate(input)) {
089            iClosure.execute(input);
090        }
091    }
092
093    /**
094     * Gets the predicate in use.
095     *
096     * @return the predicate
097     * @since 3.1
098     */
099    public Predicate<? super E> getPredicate() {
100        return iPredicate;
101    }
102
103    /**
104     * Gets the closure.
105     *
106     * @return the closure
107     * @since 3.1
108     */
109    public Closure<? super E> getClosure() {
110        return iClosure;
111    }
112
113    /**
114     * Is the loop a do-while loop.
115     *
116     * @return true is do-while, false if while
117     * @since 3.1
118     */
119    public boolean isDoLoop() {
120        return iDoLoop;
121    }
122
123}