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| 1 | +/* | |
| 2 | + * Copyright (c) 2003, 2009, Oracle and/or its affiliates. All rights reserved. | |
| 3 | + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| 4 | + * | |
| 5 | + * This code is free software; you can redistribute it and/or modify it | |
| 6 | + * under the terms of the GNU General Public License version 2 only, as | |
| 7 | + * published by the Free Software Foundation. Oracle designates this | |
| 8 | + * particular file as subject to the "Classpath" exception as provided | |
| 9 | + * by Oracle in the LICENSE file that accompanied this code. | |
| 10 | + * | |
| 11 | + * This code is distributed in the hope that it will be useful, but WITHOUT | |
| 12 | + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 13 | + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 14 | + * version 2 for more details (a copy is included in the LICENSE file that | |
| 15 | + * accompanied this code). | |
| 16 | + * | |
| 17 | + * You should have received a copy of the GNU General Public License version | |
| 18 | + * 2 along with this work; if not, write to the Free Software Foundation, | |
| 19 | + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| 20 | + * | |
| 21 | + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| 22 | + * or visit www.oracle.com if you need additional information or have any | |
| 23 | + * questions. | |
| 24 | + */ | |
| 25 | + | |
| 26 | +package java.lang; | |
| 27 | + | |
| 28 | +import java.io.Serializable; | |
| 29 | +import java.io.IOException; | |
| 30 | +import java.io.InvalidObjectException; | |
| 31 | +import java.io.ObjectInputStream; | |
| 32 | +import java.io.ObjectStreamException; | |
| 33 | + | |
| 34 | +/** | |
| 35 | + * This is the common base class of all Java language enumeration types. | |
| 36 | + * | |
| 37 | + * More information about enums, including descriptions of the | |
| 38 | + * implicitly declared methods synthesized by the compiler, can be | |
| 39 | + * found in section 8.9 of | |
| 40 | + * <cite>The Java™ Language Specification</cite>. | |
| 41 | + * | |
| 42 | + * <p> Note that when using an enumeration type as the type of a set | |
| 43 | + * or as the type of the keys in a map, specialized and efficient | |
| 44 | + * {@linkplain java.util.EnumSet set} and {@linkplain | |
| 45 | + * java.util.EnumMap map} implementations are available. | |
| 46 | + * | |
| 47 | + * @param <E> The enum type subclass | |
| 48 | + * @author Josh Bloch | |
| 49 | + * @author Neal Gafter | |
| 50 | + * @see Class#getEnumConstants() | |
| 51 | + * @see java.util.EnumSet | |
| 52 | + * @see java.util.EnumMap | |
| 53 | + * @since 1.5 | |
| 54 | + */ | |
| 55 | +public abstract class Enum<E extends Enum<E>> | |
| 56 | + implements Comparable<E>, Serializable { | |
| 57 | + /** | |
| 58 | + * The name of this enum constant, as declared in the enum declaration. | |
| 59 | + * Most programmers should use the {@link #toString} method rather than | |
| 60 | + * accessing this field. | |
| 61 | + */ | |
| 62 | + private final String name; | |
| 63 | + | |
| 64 | + /** | |
| 65 | + * Returns the name of this enum constant, exactly as declared in its | |
| 66 | + * enum declaration. | |
| 67 | + * | |
| 68 | + * <b>Most programmers should use the {@link #toString} method in | |
| 69 | + * preference to this one, as the toString method may return | |
| 70 | + * a more user-friendly name.</b> This method is designed primarily for | |
| 71 | + * use in specialized situations where correctness depends on getting the | |
| 72 | + * exact name, which will not vary from release to release. | |
| 73 | + * | |
| 74 | + * @return the name of this enum constant | |
| 75 | + */ | |
| 76 | + public final String name() { | |
| 77 | + return name; | |
| 78 | + } | |
| 79 | + | |
| 80 | + /** | |
| 81 | + * The ordinal of this enumeration constant (its position | |
| 82 | + * in the enum declaration, where the initial constant is assigned | |
| 83 | + * an ordinal of zero). | |
| 84 | + * | |
| 85 | + * Most programmers will have no use for this field. It is designed | |
| 86 | + * for use by sophisticated enum-based data structures, such as | |
| 87 | + * {@link java.util.EnumSet} and {@link java.util.EnumMap}. | |
| 88 | + */ | |
| 89 | + private final int ordinal; | |
| 90 | + | |
| 91 | + /** | |
| 92 | + * Returns the ordinal of this enumeration constant (its position | |
| 93 | + * in its enum declaration, where the initial constant is assigned | |
| 94 | + * an ordinal of zero). | |
| 95 | + * | |
| 96 | + * Most programmers will have no use for this method. It is | |
| 97 | + * designed for use by sophisticated enum-based data structures, such | |
| 98 | + * as {@link java.util.EnumSet} and {@link java.util.EnumMap}. | |
| 99 | + * | |
| 100 | + * @return the ordinal of this enumeration constant | |
| 101 | + */ | |
| 102 | + public final int ordinal() { | |
| 103 | + return ordinal; | |
| 104 | + } | |
| 105 | + | |
| 106 | + /** | |
| 107 | + * Sole constructor. Programmers cannot invoke this constructor. | |
| 108 | + * It is for use by code emitted by the compiler in response to | |
| 109 | + * enum type declarations. | |
| 110 | + * | |
| 111 | + * @param name - The name of this enum constant, which is the identifier | |
| 112 | + * used to declare it. | |
| 113 | + * @param ordinal - The ordinal of this enumeration constant (its position | |
| 114 | + * in the enum declaration, where the initial constant is assigned | |
| 115 | + * an ordinal of zero). | |
| 116 | + */ | |
| 117 | + protected Enum(String name, int ordinal) { | |
| 118 | + this.name = name; | |
| 119 | + this.ordinal = ordinal; | |
| 120 | + } | |
| 121 | + | |
| 122 | + /** | |
| 123 | + * Returns the name of this enum constant, as contained in the | |
| 124 | + * declaration. This method may be overridden, though it typically | |
| 125 | + * isn't necessary or desirable. An enum type should override this | |
| 126 | + * method when a more "programmer-friendly" string form exists. | |
| 127 | + * | |
| 128 | + * @return the name of this enum constant | |
| 129 | + */ | |
| 130 | + public String toString() { | |
| 131 | + return name; | |
| 132 | + } | |
| 133 | + | |
| 134 | + /** | |
| 135 | + * Returns true if the specified object is equal to this | |
| 136 | + * enum constant. | |
| 137 | + * | |
| 138 | + * @param other the object to be compared for equality with this object. | |
| 139 | + * @return true if the specified object is equal to this | |
| 140 | + * enum constant. | |
| 141 | + */ | |
| 142 | + public final boolean equals(Object other) { | |
| 143 | + return this==other; | |
| 144 | + } | |
| 145 | + | |
| 146 | + /** | |
| 147 | + * Returns a hash code for this enum constant. | |
| 148 | + * | |
| 149 | + * @return a hash code for this enum constant. | |
| 150 | + */ | |
| 151 | + public final int hashCode() { | |
| 152 | + return super.hashCode(); | |
| 153 | + } | |
| 154 | + | |
| 155 | + /** | |
| 156 | + * Throws CloneNotSupportedException. This guarantees that enums | |
| 157 | + * are never cloned, which is necessary to preserve their "singleton" | |
| 158 | + * status. | |
| 159 | + * | |
| 160 | + * @return (never returns) | |
| 161 | + */ | |
| 162 | + protected final Object clone() throws CloneNotSupportedException { | |
| 163 | + throw new CloneNotSupportedException(); | |
| 164 | + } | |
| 165 | + | |
| 166 | + /** | |
| 167 | + * Compares this enum with the specified object for order. Returns a | |
| 168 | + * negative integer, zero, or a positive integer as this object is less | |
| 169 | + * than, equal to, or greater than the specified object. | |
| 170 | + * | |
| 171 | + * Enum constants are only comparable to other enum constants of the | |
| 172 | + * same enum type. The natural order implemented by this | |
| 173 | + * method is the order in which the constants are declared. | |
| 174 | + */ | |
| 175 | + public final int compareTo(E o) { | |
| 176 | + Enum other = (Enum)o; | |
| 177 | + Enum self = this; | |
| 178 | + if (self.getClass() != other.getClass() && // optimization | |
| 179 | + self.getDeclaringClass() != other.getDeclaringClass()) | |
| 180 | + throw new ClassCastException(); | |
| 181 | + return self.ordinal - other.ordinal; | |
| 182 | + } | |
| 183 | + | |
| 184 | + /** | |
| 185 | + * Returns the Class object corresponding to this enum constant's | |
| 186 | + * enum type. Two enum constants e1 and e2 are of the | |
| 187 | + * same enum type if and only if | |
| 188 | + * e1.getDeclaringClass() == e2.getDeclaringClass(). | |
| 189 | + * (The value returned by this method may differ from the one returned | |
| 190 | + * by the {@link Object#getClass} method for enum constants with | |
| 191 | + * constant-specific class bodies.) | |
| 192 | + * | |
| 193 | + * @return the Class object corresponding to this enum constant's | |
| 194 | + * enum type | |
| 195 | + */ | |
| 196 | + public final Class<E> getDeclaringClass() { | |
| 197 | + Class clazz = getClass(); | |
| 198 | + Class zuper = clazz.getSuperclass(); | |
| 199 | + return (zuper == Enum.class) ? clazz : zuper; | |
| 200 | + } | |
| 201 | + | |
| 202 | + /** | |
| 203 | + * Returns the enum constant of the specified enum type with the | |
| 204 | + * specified name. The name must match exactly an identifier used | |
| 205 | + * to declare an enum constant in this type. (Extraneous whitespace | |
| 206 | + * characters are not permitted.) | |
| 207 | + * | |
| 208 | + * <p>Note that for a particular enum type {@code T}, the | |
| 209 | + * implicitly declared {@code public static T valueOf(String)} | |
| 210 | + * method on that enum may be used instead of this method to map | |
| 211 | + * from a name to the corresponding enum constant. All the | |
| 212 | + * constants of an enum type can be obtained by calling the | |
| 213 | + * implicit {@code public static T[] values()} method of that | |
| 214 | + * type. | |
| 215 | + * | |
| 216 | + * @param <T> The enum type whose constant is to be returned | |
| 217 | + * @param enumType the {@code Class} object of the enum type from which | |
| 218 | + * to return a constant | |
| 219 | + * @param name the name of the constant to return | |
| 220 | + * @return the enum constant of the specified enum type with the | |
| 221 | + * specified name | |
| 222 | + * @throws IllegalArgumentException if the specified enum type has | |
| 223 | + * no constant with the specified name, or the specified | |
| 224 | + * class object does not represent an enum type | |
| 225 | + * @throws NullPointerException if {@code enumType} or {@code name} | |
| 226 | + * is null | |
| 227 | + * @since 1.5 | |
| 228 | + */ | |
| 229 | + public static <T extends Enum<T>> T valueOf(Class<T> enumType, | |
| 230 | + String name) { | |
| 231 | + T result = enumType.enumConstantDirectory().get(name); | |
| 232 | + if (result != null) | |
| 233 | + return result; | |
| 234 | + if (name == null) | |
| 235 | + throw new NullPointerException("Name is null"); | |
| 236 | + throw new IllegalArgumentException( | |
| 237 | + "No enum constant " + enumType.getCanonicalName() + "." + name); | |
| 238 | + } | |
| 239 | + | |
| 240 | + /** | |
| 241 | + * enum classes cannot have finalize methods. | |
| 242 | + */ | |
| 243 | + protected final void finalize() { } | |
| 244 | + | |
| 245 | + /** | |
| 246 | + * prevent default deserialization | |
| 247 | + */ | |
| 248 | + private void readObject(ObjectInputStream in) throws IOException, | |
| 249 | + ClassNotFoundException { | |
| 250 | + throw new InvalidObjectException("can't deserialize enum"); | |
| 251 | + } | |
| 252 | + | |
| 253 | + private void readObjectNoData() throws ObjectStreamException { | |
| 254 | + throw new InvalidObjectException("can't deserialize enum"); | |
| 255 | + } | |
| 256 | +} | |