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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 | } | ||