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Ant example source code file (Enumerations.java)

This example Ant source code file (Enumerations.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 - Ant tags/keywords

arrayenumeration, compoundenumeration, compoundenumeration, enumeration, enumeration, enumerations, nosuchelementexception, nosuchelementexception, object, object, util

The Enumerations.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.tools.ant.taskdefs.optional.junit;

import java.util.Enumeration;
import java.util.NoSuchElementException;

/**
 * A couple of methods related to enumerations that might be useful.
 * This class should probably disappear once the required JDK is set to 1.2
 * instead of 1.1.
 *
 */
public final class Enumerations {

        private Enumerations() {
        }

        /**
         * creates an enumeration from an array of objects.
         * @param       array   the array of object to enumerate.
         * @return the enumeration over the array of objects.
         */
        public static Enumeration fromArray(Object[] array) {
                return new ArrayEnumeration(array);
        }

        /**
        * creates an enumeration from an array of enumeration. The created enumeration
        * will sequentially enumerate over all elements of each enumeration and skip
        * <tt>null enumeration elements in the array.
        * @param        enums   the array of enumerations.
        * @return the enumeration over the array of enumerations.
         */
        public static Enumeration fromCompound(Enumeration[] enums) {
                return new CompoundEnumeration(enums);
        }

}


/**
 * Convenient enumeration over an array of objects.
 */
class ArrayEnumeration implements Enumeration {

        /** object array */
        private Object[] array;

        /** current index */
        private int pos;

        /**
         * Initialize a new enumeration that wraps an array.
         * @param       array   the array of object to enumerate.
         */
        public ArrayEnumeration(Object[] array) {
                this.array = array;
                this.pos = 0;
        }
        /**
         * Tests if this enumeration contains more elements.
         *
         * @return  <code>true if and only if this enumeration object
         *           contains at least one more element to provide;
         *          <code>false otherwise.
         */
        public boolean hasMoreElements() {
                return (pos < array.length);
        }

        /**
         * Returns the next element of this enumeration if this enumeration
         * object has at least one more element to provide.
         *
         * @return     the next element of this enumeration.
         * @throws  NoSuchElementException  if no more elements exist.
         */
        public Object nextElement() throws NoSuchElementException {
                if (hasMoreElements()) {
                        Object o = array[pos];
                        pos++;
                        return o;
                }
                throw new NoSuchElementException();
        }
}
/**
 * Convenient enumeration over an array of enumeration. For example:
 * <pre>
 * Enumeration e1 = v1.elements();
 * while (e1.hasMoreElements()) {
 *    // do something
 * }
 * Enumeration e2 = v2.elements();
 * while (e2.hasMoreElements()) {
 *    // do the same thing
 * }
 * </pre>
 * can be written as:
 * <pre>
 * Enumeration[] enums = { v1.elements(), v2.elements() };
 * Enumeration e = Enumerations.fromCompound(enums);
 * while (e.hasMoreElements()) {
 *    // do something
 * }
 * </pre>
 * Note that the enumeration will skip null elements in the array. The following is
 * thus possible:
 * <pre>
 * Enumeration[] enums = { v1.elements(), null, v2.elements() }; // a null enumeration in the array
 * Enumeration e = Enumerations.fromCompound(enums);
 * while (e.hasMoreElements()) {
 *    // do something
 * }
 * </pre>
 */
 class CompoundEnumeration implements Enumeration {

        /** enumeration array */
        private Enumeration[] enumArray;

        /** index in the enums array */
        private int index = 0;

    public CompoundEnumeration(Enumeration[] enumarray) {
                this.enumArray = enumarray;
    }

        /**
         * Tests if this enumeration contains more elements.
         *
         * @return  <code>true if and only if this enumeration object
         *           contains at least one more element to provide;
         *          <code>false otherwise.
         */
    public boolean hasMoreElements() {
                while (index < enumArray.length) {
                        if (enumArray[index] != null && enumArray[index].hasMoreElements()) {
                                return true;
                        }
                        index++;
                }
                return false;
    }

        /**
         * Returns the next element of this enumeration if this enumeration
         * object has at least one more element to provide.
         *
         * @return     the next element of this enumeration.
         * @throws  NoSuchElementException  if no more elements exist.
         */
    public Object nextElement() throws NoSuchElementException {
                if (hasMoreElements()) {
                        return enumArray[index].nextElement();
                }
                throw new NoSuchElementException();
    }
}


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