    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     */
    017    package org.apache.commons.lang.enum;
    018
    019    import java.util.Iterator;
    020    import java.util.List;
    021
    022    import org.apache.commons.lang.ClassUtils;
    023
    024    /**
    025     * <p>Abstract superclass for type-safe enums with integer values suitable
    026     * for use in <code>switch</code> statements.</p>
    027     *
    028     * <p><em>NOTE:</em>Due to the way in which Java ClassLoaders work, comparing
    029     * <code>Enum</code> objects should always be done using the equals() method,
    030     * not <code>==</code>. The equals() method will try <code>==</code> first so
    031     * in most cases the effect is the same.</p>
    032     *
    033     * <p>To use this class, it must be subclassed. For example:</p>
    034     *
    035     * <pre>
    036     * public final class JavaVersionEnum extends ValuedEnum {
    037     *   //standard enums for version of JVM
    038     *   public static final int  JAVA1_0_VALUE  = 100;
    039     *   public static final int  JAVA1_1_VALUE  = 110;
    040     *   public static final int  JAVA1_2_VALUE  = 120;
    041     *   public static final int  JAVA1_3_VALUE  = 130;
    042     *   public static final JavaVersionEnum  JAVA1_0  = new JavaVersionEnum( "Java 1.0", JAVA1_0_VALUE );
    043     *   public static final JavaVersionEnum  JAVA1_1  = new JavaVersionEnum( "Java 1.1", JAVA1_1_VALUE );
    044     *   public static final JavaVersionEnum  JAVA1_2  = new JavaVersionEnum( "Java 1.2", JAVA1_2_VALUE );
    045     *   public static final JavaVersionEnum  JAVA1_3  = new JavaVersionEnum( "Java 1.3", JAVA1_3_VALUE );
    046     *
    047     *   private JavaVersionEnum(String name, int value) {
    048     *     super( name, value );
    049     *   }
    050     *
    051     *   public static JavaVersionEnum getEnum(String javaVersion) {
    052     *     return (JavaVersionEnum) getEnum(JavaVersionEnum.class, javaVersion);
    053     *   }
    054     *
    055     *   public static JavaVersionEnum getEnum(int javaVersion) {
    056     *     return (JavaVersionEnum) getEnum(JavaVersionEnum.class, javaVersion);
    057     *   }
    058     *
    059     *   public static Map getEnumMap() {
    060     *     return getEnumMap(JavaVersionEnum.class);
    061     *   }
    062     *
    063     *   public static List getEnumList() {
    064     *     return getEnumList(JavaVersionEnum.class);
    065     *   }
    066     *
    067     *   public static Iterator iterator() {
    068     *     return iterator(JavaVersionEnum.class);
    069     *   }
    070     * }
    071     * </pre>
    072     *
    073     * <p>The above class could then be used as follows:</p>
    074     *
    075     * <pre>
    076     * public void doSomething(JavaVersionEnum ver) {
    077     *   switch (ver.getValue()) {
    078     *     case JAVA1_0_VALUE:
    079     *       // ...
    080     *       break;
    081     *     case JAVA1_1_VALUE:
    082     *       // ...
    083     *       break;
    084     *     //...
    085     *   }
    086     * }
    087     * </pre>
    088     *
    089     * <p>As shown, each enum has a name and a value. These can be accessed using
    090     * <code>getName</code> and <code>getValue</code>.</p>
    091     *
    092     * <p>The <code>getEnum</code> and <code>iterator</code> methods are recommended.
    093     * Unfortunately, Java restrictions require these to be coded as shown in each subclass.
    094     * An alternative choice is to use the {@link EnumUtils} class.</p>
    095     *
    096     * @deprecated Replaced by {@link org.apache.commons.lang.enums.ValuedEnum org.apache.commons.lang.enums.ValuedEnum}
    097     *          and will be removed in version 3.0. All classes in this package are deprecated and repackaged to
    098     *          {@link org.apache.commons.lang.enums} since <code>enum</code> is a Java 1.5 keyword.
    099     * @see org.apache.commons.lang.enums.ValuedEnum
    100     * @author Apache Avalon project
    101     * @author Apache Software Foundation
    102     * @since 1.0
    103     * @version $Id: ValuedEnum.java 905636 2010-02-02 14:03:32Z niallp $
    104     */
    105    public abstract class ValuedEnum extends Enum {
    106
    107        /**
    108         * Required for serialization support. Lang version 1.0.1 serial compatibility.
    109         *
    110         * @see java.io.Serializable
    111         */
    112        private static final long serialVersionUID = -7129650521543789085L;
    113
    114        /**
    115         * The value contained in enum.
    116         */
    117        private final int iValue;
    118
    119        /**
    120         * Constructor for enum item.
    121         *
    122         * @param name  the name of enum item
    123         * @param value  the value of enum item
    124         */
    125        protected ValuedEnum(String name, int value) {
    126            super(name);
    127            iValue = value;
    128        }
    129
    130        /**
    131         * <p>Gets an <code>Enum</code> object by class and value.</p>
    132         *
    133         * <p>This method loops through the list of <code>Enum</code>,
    134         * thus if there are many <code>Enum</code>s this will be
    135         * slow.</p>
    136         *
    137         * @param enumClass  the class of the <code>Enum</code> to get
    138         * @param value  the value of the <code>Enum</code> to get
    139         * @return the enum object, or null if the enum does not exist
    140         * @throws IllegalArgumentException if the enum class is <code>null</code>
    141         */
    142        protected static Enum getEnum(Class enumClass, int value) {
    143            if (enumClass == null) {
    144                throw new IllegalArgumentException("The Enum Class must not be null");
    145            }
    146            List list = Enum.getEnumList(enumClass);
    147            for (Iterator it = list.iterator(); it.hasNext();) {
    148                ValuedEnum enumeration = (ValuedEnum) it.next();
    149                if (enumeration.getValue() == value) {
    150                    return enumeration;
    151                }
    152            }
    153            return null;
    154        }
    155
    156        /**
    157         * <p>Get value of enum item.</p>
    158         *
    159         * @return the enum item's value.
    160         */
    161        public final int getValue() {
    162            return iValue;
    163        }
    164
    165        /**
    166         * <p>Tests for order.</p>
    167         *
    168         * <p>The default ordering is numeric by value, but this
    169         * can be overridden by subclasses.</p>
    170         *
    171         * @see java.lang.Comparable#compareTo(Object)
    172         * @param other  the other object to compare to
    173         * @return -ve if this is less than the other object, +ve if greater than,
    174         *  <code>0</code> of equal
    175         * @throws ClassCastException if other is not an <code>Enum</code>
    176         * @throws NullPointerException if other is <code>null</code>
    177         */
    178        public int compareTo(Object other) {
    179            return iValue - ((ValuedEnum) other).iValue;
    180        }
    181
    182        /**
    183         * <p>Human readable description of this <code>Enum</code> item.</p>
    184         *
    185         * @return String in the form <code>type[name=value]</code>, for example:
    186         *  <code>JavaVersion[Java 1.0=100]</code>. Note that the package name is
    187         *  stripped from the type name.
    188         */
    189        public String toString() {
    190            if (iToString == null) {
    191                String shortName = ClassUtils.getShortClassName(getEnumClass());
    192                iToString = shortName + "[" + getName() + "=" + getValue() + "]";
    193            }
    194            return iToString;
    195        }
    196    }