Commons Collections example source code file (WhileClosure.java)

This example Commons Collections source code file (WhileClosure.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons Collections tags/keywords

closure, closure, illegalargumentexception, illegalargumentexception, io, predicate, predicate, serializable, whileclosure, whileclosure

The Commons Collections WhileClosure.java source code

/*
 *  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.collections.functors;

import java.io.Serializable;

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

/**
 * Closure implementation that executes a closure repeatedly until a condition is met,
 * like a do-while or while loop.
 * 
 * @since Commons Collections 3.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 *
 * @author Stephen Colebourne
 */
public class WhileClosure implements Closure, Serializable {

    /** Serial version UID */
    private static final long serialVersionUID = -3110538116913760108L;

    /** The test condition */
    private final Predicate iPredicate;
    /** The closure to call */
    private final Closure iClosure;
    /** The flag, true is a do loop, false is a while */
    private final boolean iDoLoop;

    /**
     * Factory method that performs validation.
     * 
     * @param predicate  the predicate used to evaluate when the loop terminates, not null
     * @param closure  the closure the execute, not null
     * @param doLoop  true to act as a do-while loop, always executing the closure once
     * @return the <code>while closure
     * @throws IllegalArgumentException if the predicate or closure is null
     */
    public static Closure getInstance(Predicate predicate, Closure closure, boolean doLoop) {
        if (predicate == null) {
            throw new IllegalArgumentException("Predicate must not be null");
        }
        if (closure == null) {
            throw new IllegalArgumentException("Closure must not be null");
        }
        return new WhileClosure(predicate, closure, doLoop);
    }

    /**
     * Constructor that performs no validation.
     * Use <code>getInstance if you want that.
     * 
     * @param predicate  the predicate used to evaluate when the loop terminates, not null
     * @param closure  the closure the execute, not null
     * @param doLoop  true to act as a do-while loop, always executing the closure once
     */
    public WhileClosure(Predicate predicate, Closure closure, boolean doLoop) {
        super();
        iPredicate = predicate;
        iClosure = closure;
        iDoLoop = doLoop;
    }

    /**
     * Executes the closure until the predicate is false.
     * 
     * @param input  the input object
     */
    public void execute(Object input) {
        if (iDoLoop) {
            iClosure.execute(input);
        }
        while (iPredicate.evaluate(input)) {
            iClosure.execute(input);
        }
    }

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

    /**
     * Gets the closure.
     * 
     * @return the closure
     * @since Commons Collections 3.1
     */
    public Closure getClosure() {
        return iClosure;
    }

    /**
     * Is the loop a do-while loop.
     * 
     * @return true is do-while, false if while
     * @since Commons Collections 3.1
     */
    public boolean isDoLoop() {
        return iDoLoop;
    }

}