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commons-lang-2.6.jar - Apache Commons Lang
commons-lang-2.6.jar is the JAR file for Apache Commons Lang 2.6, which provides a host of helper utilities for the java.lang API.
JAR File Size and Download Location:
File name: commons-lang-2.6.jar File size: 284220 bytes Date modified: 01/13/2011 Download: Apache Commons Lang Website
✍: FYIcenter
⏎ org/apache/commons/lang/enum/Enum.java
/* * 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.lang.enum; import java.io.Serializable; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.ArrayList; import java.util.Collections; import java.util.HashMap; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.WeakHashMap; import org.apache.commons.lang.ClassUtils; import org.apache.commons.lang.StringUtils; /** * <p>Abstract superclass for type-safe enums.</p> * * <p>One feature of the C programming language lacking in Java is enumerations. The * C implementation based on ints was poor and open to abuse. The original Java * recommendation and most of the JDK also uses int constants. It has been recognised * however that a more robust type-safe class-based solution can be designed. This * class follows the basic Java type-safe enumeration pattern.</p> * * <p><em>NOTE:</em>Due to the way in which Java ClassLoaders work, comparing * Enum objects should always be done using <code>equals()</code>, not <code>==</code>. * The equals() method will try == first so in most cases the effect is the same.</p> * * <p>Of course, if you actually want (or don't mind) Enums in different class * loaders being non-equal, then you can use <code>==</code>.</p> * * <h4>Simple Enums</h4> * * <p>To use this class, it must be subclassed. For example:</p> * * <pre> * public final class ColorEnum extends Enum { * public static final ColorEnum RED = new ColorEnum("Red"); * public static final ColorEnum GREEN = new ColorEnum("Green"); * public static final ColorEnum BLUE = new ColorEnum("Blue"); * * private ColorEnum(String color) { * super(color); * } * * public static ColorEnum getEnum(String color) { * return (ColorEnum) getEnum(ColorEnum.class, color); * } * * public static Map getEnumMap() { * return getEnumMap(ColorEnum.class); * } * * public static List getEnumList() { * return getEnumList(ColorEnum.class); * } * * public static Iterator iterator() { * return iterator(ColorEnum.class); * } * } * </pre> * * <p>As shown, each enum has a name. This can be accessed using <code>getName</code>.</p> * * <p>The <code>getEnum</code> and <code>iterator</code> methods are recommended. * Unfortunately, Java restrictions require these to be coded as shown in each subclass. * An alternative choice is to use the {@link EnumUtils} class.</p> * * <h4>Subclassed Enums</h4> * <p>A hierarchy of Enum classes can be built. In this case, the superclass is * unaffected by the addition of subclasses (as per normal Java). The subclasses * may add additional Enum constants <em>of the type of the superclass</em>. The * query methods on the subclass will return all of the Enum constants from the * superclass and subclass.</p> * * <pre> * public final class ExtraColorEnum extends ColorEnum { * // NOTE: Color enum declared above is final, change that to get this * // example to compile. * public static final ColorEnum YELLOW = new ExtraColorEnum("Yellow"); * * private ExtraColorEnum(String color) { * super(color); * } * * public static ColorEnum getEnum(String color) { * return (ColorEnum) getEnum(ExtraColorEnum.class, color); * } * * public static Map getEnumMap() { * return getEnumMap(ExtraColorEnum.class); * } * * public static List getEnumList() { * return getEnumList(ExtraColorEnum.class); * } * * public static Iterator iterator() { * return iterator(ExtraColorEnum.class); * } * } * </pre> * * <p>This example will return RED, GREEN, BLUE, YELLOW from the List and iterator * methods in that order. The RED, GREEN and BLUE instances will be the same (==) * as those from the superclass ColorEnum. Note that YELLOW is declared as a * ColorEnum and not an ExtraColorEnum.</p> * * <h4>Functional Enums</h4> * * <p>The enums can have functionality by defining subclasses and * overriding the <code>getEnumClass()</code> method:</p> * * <pre> * public static final OperationEnum PLUS = new PlusOperation(); * private static final class PlusOperation extends OperationEnum { * private PlusOperation() { * super("Plus"); * } * public int eval(int a, int b) { * return a + b; * } * } * public static final OperationEnum MINUS = new MinusOperation(); * private static final class MinusOperation extends OperationEnum { * private MinusOperation() { * super("Minus"); * } * public int eval(int a, int b) { * return a - b; * } * } * * private OperationEnum(String color) { * super(color); * } * * public final Class getEnumClass() { // NOTE: new method! * return OperationEnum.class; * } * * public abstract double eval(double a, double b); * * public static OperationEnum getEnum(String name) { * return (OperationEnum) getEnum(OperationEnum.class, name); * } * * public static Map getEnumMap() { * return getEnumMap(OperationEnum.class); * } * * public static List getEnumList() { * return getEnumList(OperationEnum.class); * } * * public static Iterator iterator() { * return iterator(OperationEnum.class); * } * } * </pre> * <p>The code above will work on JDK 1.2. If JDK1.3 and later is used, * the subclasses may be defined as anonymous.</p> * * <h4>Nested class Enums</h4> * * <p>Care must be taken with class loading when defining a static nested class * for enums. The static nested class can be loaded without the surrounding outer * class being loaded. This can result in an empty list/map/iterator being returned. * One solution is to define a static block that references the outer class where * the constants are defined. For example:</p> * * <pre> * public final class Outer { * public static final BWEnum BLACK = new BWEnum("Black"); * public static final BWEnum WHITE = new BWEnum("White"); * * // static nested enum class * public static final class BWEnum extends Enum { * * static { * // explicitly reference BWEnum class to force constants to load * Object obj = Outer.BLACK; * } * * // ... other methods omitted * } * } * </pre> * * <p>Although the above solves the problem, it is not recommended. The best solution * is to define the constants in the enum class, and hold references in the outer class: * * <pre> * public final class Outer { * public static final BWEnum BLACK = BWEnum.BLACK; * public static final BWEnum WHITE = BWEnum.WHITE; * * // static nested enum class * public static final class BWEnum extends Enum { * // only define constants in enum classes - private if desired * private static final BWEnum BLACK = new BWEnum("Black"); * private static final BWEnum WHITE = new BWEnum("White"); * * // ... other methods omitted * } * } * </pre> * * <p>For more details, see the 'Nested' test cases. * * @deprecated Replaced by {@link org.apache.commons.lang.enums.Enum org.apache.commons.lang.enums.Enum} * and will be removed in version 3.0. All classes in this package are deprecated and repackaged to * {@link org.apache.commons.lang.enums} since <code>enum</code> is a Java 1.5 keyword. * @see org.apache.commons.lang.enums.Enum * @author Apache Avalon project * @author Apache Software Foundation * @author Chris Webb * @author Mike Bowler * @since 1.0 * @version $Id: Enum.java 912394 2010-02-21 20:16:22Z niallp $ */ public abstract class Enum implements Comparable, Serializable { /** * Required for serialization support. Lang version 1.0.1 serial compatibility. * * @see java.io.Serializable */ private static final long serialVersionUID = -487045951170455942L; // After discussion, the default size for HashMaps is used, as the // sizing algorithm changes across the JDK versions /** * An empty <code>Map</code>, as JDK1.2 didn't have an empty map. */ private static final Map EMPTY_MAP = Collections.unmodifiableMap(new HashMap(0)); /** * <code>Map</code>, key of class name, value of <code>Entry</code>. */ private static Map cEnumClasses // LANG-334: To avoid exposing a mutating map, // we copy it each time we add to it. This is cheaper than // using a synchronized map since we are almost entirely reads = new WeakHashMap(); /** * The string representation of the Enum. */ private final String iName; /** * The hashcode representation of the Enum. */ private transient final int iHashCode; /** * The toString representation of the Enum. * @since 2.0 */ protected transient String iToString = null; /** * <p>Enable the iterator to retain the source code order.</p> */ private static class Entry { /** * Map of Enum name to Enum. */ final Map map = new HashMap(); /** * Map of Enum name to Enum. */ final Map unmodifiableMap = Collections.unmodifiableMap(map); /** * List of Enums in source code order. */ final List list = new ArrayList(25); /** * Map of Enum name to Enum. */ final List unmodifiableList = Collections.unmodifiableList(list); /** * <p>Restrictive constructor.</p> */ protected Entry() { super(); } } /** * <p>Constructor to add a new named item to the enumeration.</p> * * @param name the name of the enum object, * must not be empty or <code>null</code> * @throws IllegalArgumentException if the name is <code>null</code> * or an empty string * @throws IllegalArgumentException if the getEnumClass() method returns * a null or invalid Class */ protected Enum(String name) { super(); init(name); iName = name; iHashCode = 7 + getEnumClass().hashCode() + 3 * name.hashCode(); // cannot create toString here as subclasses may want to include other data } /** * Initializes the enumeration. * * @param name the enum name * @throws IllegalArgumentException if the name is null or empty or duplicate * @throws IllegalArgumentException if the enumClass is null or invalid */ private void init(String name) { if (StringUtils.isEmpty(name)) { throw new IllegalArgumentException("The Enum name must not be empty or null"); } Class enumClass = getEnumClass(); if (enumClass == null) { throw new IllegalArgumentException("getEnumClass() must not be null"); } Class cls = getClass(); boolean ok = false; while (cls != null && cls != Enum.class && cls != ValuedEnum.class) { if (cls == enumClass) { ok = true; break; } cls = cls.getSuperclass(); } if (ok == false) { throw new IllegalArgumentException("getEnumClass() must return a superclass of this class"); } Entry entry; synchronized( Enum.class ) { // LANG-334 // create entry entry = (Entry) cEnumClasses.get(enumClass); if (entry == null) { entry = createEntry(enumClass); Map myMap = new WeakHashMap( ); // we avoid the (Map) constructor to achieve JDK 1.2 support myMap.putAll( cEnumClasses ); myMap.put(enumClass, entry); cEnumClasses = myMap; } } if (entry.map.containsKey(name)) { throw new IllegalArgumentException("The Enum name must be unique, '" + name + "' has already been added"); } entry.map.put(name, this); entry.list.add(this); } /** * <p>Handle the deserialization of the class to ensure that multiple * copies are not wastefully created, or illegal enum types created.</p> * * @return the resolved object */ protected Object readResolve() { Entry entry = (Entry) cEnumClasses.get(getEnumClass()); if (entry == null) { return null; } return entry.map.get(getName()); } //-------------------------------------------------------------------------------- /** * <p>Gets an <code>Enum</code> object by class and name.</p> * * @param enumClass the class of the Enum to get, must not * be <code>null</code> * @param name the name of the <code>Enum</code> to get, * may be <code>null</code> * @return the enum object, or <code>null</code> if the enum does not exist * @throws IllegalArgumentException if the enum class * is <code>null</code> */ protected static Enum getEnum(Class enumClass, String name) { Entry entry = getEntry(enumClass); if (entry == null) { return null; } return (Enum) entry.map.get(name); } /** * <p>Gets the <code>Map</code> of <code>Enum</code> objects by * name using the <code>Enum</code> class.</p> * * <p>If the requested class has no enum objects an empty * <code>Map</code> is returned.</p> * * @param enumClass the class of the <code>Enum</code> to get, * must not be <code>null</code> * @return the enum object Map * @throws IllegalArgumentException if the enum class is <code>null</code> * @throws IllegalArgumentException if the enum class is not a subclass of Enum */ protected static Map getEnumMap(Class enumClass) { Entry entry = getEntry(enumClass); if (entry == null) { return EMPTY_MAP; } return entry.unmodifiableMap; } /** * <p>Gets the <code>List</code> of <code>Enum</code> objects using the * <code>Enum</code> class.</p> * * <p>The list is in the order that the objects were created (source code order). * If the requested class has no enum objects an empty <code>List</code> is * returned.</p> * * @param enumClass the class of the <code>Enum</code> to get, * must not be <code>null</code> * @return the enum object Map * @throws IllegalArgumentException if the enum class is <code>null</code> * @throws IllegalArgumentException if the enum class is not a subclass of Enum */ protected static List getEnumList(Class enumClass) { Entry entry = getEntry(enumClass); if (entry == null) { return Collections.EMPTY_LIST; } return entry.unmodifiableList; } /** * <p>Gets an <code>Iterator</code> over the <code>Enum</code> objects in * an <code>Enum</code> class.</p> * * <p>The <code>Iterator</code> is in the order that the objects were * created (source code order). If the requested class has no enum * objects an empty <code>Iterator</code> is returned.</p> * * @param enumClass the class of the <code>Enum</code> to get, * must not be <code>null</code> * @return an iterator of the Enum objects * @throws IllegalArgumentException if the enum class is <code>null</code> * @throws IllegalArgumentException if the enum class is not a subclass of Enum */ protected static Iterator iterator(Class enumClass) { return Enum.getEnumList(enumClass).iterator(); } //----------------------------------------------------------------------- /** * <p>Gets an <code>Entry</code> from the map of Enums.</p> * * @param enumClass the class of the <code>Enum</code> to get * @return the enum entry */ private static Entry getEntry(Class enumClass) { if (enumClass == null) { throw new IllegalArgumentException("The Enum Class must not be null"); } if (Enum.class.isAssignableFrom(enumClass) == false) { throw new IllegalArgumentException("The Class must be a subclass of Enum"); } Entry entry = (Entry) cEnumClasses.get(enumClass); if (entry == null) { try { // LANG-76 - try to force class initialization for JDK 1.5+ Class.forName(enumClass.getName(), true, enumClass.getClassLoader()); entry = (Entry) cEnumClasses.get(enumClass); } catch (Exception e) { // Ignore } } return entry; } /** * <p>Creates an <code>Entry</code> for storing the Enums.</p> * * <p>This accounts for subclassed Enums.</p> * * @param enumClass the class of the <code>Enum</code> to get * @return the enum entry */ private static Entry createEntry(Class enumClass) { Entry entry = new Entry(); Class cls = enumClass.getSuperclass(); while (cls != null && cls != Enum.class && cls != ValuedEnum.class) { Entry loopEntry = (Entry) cEnumClasses.get(cls); if (loopEntry != null) { entry.list.addAll(loopEntry.list); entry.map.putAll(loopEntry.map); break; // stop here, as this will already have had superclasses added } cls = cls.getSuperclass(); } return entry; } //----------------------------------------------------------------------- /** * <p>Retrieve the name of this Enum item, set in the constructor.</p> * * @return the <code>String</code> name of this Enum item */ public final String getName() { return iName; } /** * <p>Retrieves the Class of this Enum item, set in the constructor.</p> * * <p>This is normally the same as <code>getClass()</code>, but for * advanced Enums may be different. If overridden, it must return a * constant value.</p> * * @return the <code>Class</code> of the enum * @since 2.0 */ public Class getEnumClass() { return getClass(); } /** * <p>Tests for equality.</p> * * <p>Two Enum objects are considered equal * if they have the same class names and the same names. * Identity is tested for first, so this method usually runs fast.</p> * * <p>If the parameter is in a different class loader than this instance, * reflection is used to compare the names.</p> * * @param other the other object to compare for equality * @return <code>true</code> if the Enums are equal */ public final boolean equals(Object other) { if (other == this) { return true; } else if (other == null) { return false; } else if (other.getClass() == this.getClass()) { // Ok to do a class cast to Enum here since the test above // guarantee both // classes are in the same class loader. return iName.equals(((Enum) other).iName); } else { // This and other are in different class loaders, we must check indirectly if (other.getClass().getName().equals(this.getClass().getName()) == false) { return false; } return iName.equals( getNameInOtherClassLoader(other) ); } } /** * <p>Returns a suitable hashCode for the enumeration.</p> * * @return a hashcode based on the name */ public final int hashCode() { return iHashCode; } /** * <p>Tests for order.</p> * * <p>The default ordering is alphabetic by name, but this * can be overridden by subclasses.</p> * * <p>If the parameter is in a different class loader than this instance, * reflection is used to compare the names.</p> * * @see java.lang.Comparable#compareTo(Object) * @param other the other object to compare to * @return -ve if this is less than the other object, +ve if greater * than, <code>0</code> of equal * @throws ClassCastException if other is not an Enum * @throws NullPointerException if other is <code>null</code> */ public int compareTo(Object other) { if (other == this) { return 0; } if (other.getClass() != this.getClass()) { if (other.getClass().getName().equals(this.getClass().getName())) { return iName.compareTo( getNameInOtherClassLoader(other) ); } throw new ClassCastException( "Different enum class '" + ClassUtils.getShortClassName(other.getClass()) + "'"); } return iName.compareTo(((Enum) other).iName); } /** * <p>Use reflection to return an objects class name.</p> * * @param other The object to determine the class name for * @return The class name */ private String getNameInOtherClassLoader(Object other) { try { Method mth = other.getClass().getMethod("getName", null); String name = (String) mth.invoke(other, null); return name; } catch (NoSuchMethodException e) { // ignore - should never happen } catch (IllegalAccessException e) { // ignore - should never happen } catch (InvocationTargetException e) { // ignore - should never happen } throw new IllegalStateException("This should not happen"); } /** * <p>Human readable description of this Enum item.</p> * * @return String in the form <code>type[name]</code>, for example: * <code>Color[Red]</code>. Note that the package name is stripped from * the type name. */ public String toString() { if (iToString == null) { String shortName = ClassUtils.getShortClassName(getEnumClass()); iToString = shortName + "[" + getName() + "]"; } return iToString; } }
⏎ org/apache/commons/lang/enum/Enum.java
⇒ commons-lang-1.0.1.jar - Apache Commons Lang
⇐ What Is commons-lang3-3.1.jar
2009-12-24, 80067👍, 0💬
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