001: /*
002: * Copyright 2003-2007 Sun Microsystems, Inc. All Rights Reserved.
003: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004: *
005: * This code is free software; you can redistribute it and/or modify it
006: * under the terms of the GNU General Public License version 2 only, as
007: * published by the Free Software Foundation. Sun designates this
008: * particular file as subject to the "Classpath" exception as provided
009: * by Sun in the LICENSE file that accompanied this code.
010: *
011: * This code is distributed in the hope that it will be useful, but WITHOUT
012: * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013: * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014: * version 2 for more details (a copy is included in the LICENSE file that
015: * accompanied this code).
016: *
017: * You should have received a copy of the GNU General Public License version
018: * 2 along with this work; if not, write to the Free Software Foundation,
019: * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020: *
021: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022: * CA 95054 USA or visit www.sun.com if you need additional information or
023: * have any questions.
024: */
025:
026: package java.lang;
027:
028: import java.io.Serializable;
029: import java.io.IOException;
030: import java.io.InvalidObjectException;
031: import java.io.ObjectInputStream;
032: import java.io.ObjectStreamException;
033:
034: /**
035: * This is the common base class of all Java language enumeration types.
036: *
037: * @author Josh Bloch
038: * @author Neal Gafter
039: * @version 1.24, 05/05/07
040: * @see Class#getEnumConstants()
041: * @since 1.5
042: */
043: public abstract class Enum<E extends Enum<E>> implements Comparable<E>,
044: Serializable {
045: /**
046: * The name of this enum constant, as declared in the enum declaration.
047: * Most programmers should use the {@link #toString} method rather than
048: * accessing this field.
049: */
050: private final String name;
051:
052: /**
053: * Returns the name of this enum constant, exactly as declared in its
054: * enum declaration.
055: *
056: * <b>Most programmers should use the {@link #toString} method in
057: * preference to this one, as the toString method may return
058: * a more user-friendly name.</b> This method is designed primarily for
059: * use in specialized situations where correctness depends on getting the
060: * exact name, which will not vary from release to release.
061: *
062: * @return the name of this enum constant
063: */
064: public final String name() {
065: return name;
066: }
067:
068: /**
069: * The ordinal of this enumeration constant (its position
070: * in the enum declaration, where the initial constant is assigned
071: * an ordinal of zero).
072: *
073: * Most programmers will have no use for this field. It is designed
074: * for use by sophisticated enum-based data structures, such as
075: * {@link java.util.EnumSet} and {@link java.util.EnumMap}.
076: */
077: private final int ordinal;
078:
079: /**
080: * Returns the ordinal of this enumeration constant (its position
081: * in its enum declaration, where the initial constant is assigned
082: * an ordinal of zero).
083: *
084: * Most programmers will have no use for this method. It is
085: * designed for use by sophisticated enum-based data structures, such
086: * as {@link java.util.EnumSet} and {@link java.util.EnumMap}.
087: *
088: * @return the ordinal of this enumeration constant
089: */
090: public final int ordinal() {
091: return ordinal;
092: }
093:
094: /**
095: * Sole constructor. Programmers cannot invoke this constructor.
096: * It is for use by code emitted by the compiler in response to
097: * enum type declarations.
098: *
099: * @param name - The name of this enum constant, which is the identifier
100: * used to declare it.
101: * @param ordinal - The ordinal of this enumeration constant (its position
102: * in the enum declaration, where the initial constant is assigned
103: * an ordinal of zero).
104: */
105: protected Enum(String name, int ordinal) {
106: this .name = name;
107: this .ordinal = ordinal;
108: }
109:
110: /**
111: * Returns the name of this enum constant, as contained in the
112: * declaration. This method may be overridden, though it typically
113: * isn't necessary or desirable. An enum type should override this
114: * method when a more "programmer-friendly" string form exists.
115: *
116: * @return the name of this enum constant
117: */
118: public String toString() {
119: return name;
120: }
121:
122: /**
123: * Returns true if the specified object is equal to this
124: * enum constant.
125: *
126: * @param other the object to be compared for equality with this object.
127: * @return true if the specified object is equal to this
128: * enum constant.
129: */
130: public final boolean equals(Object other) {
131: return this == other;
132: }
133:
134: /**
135: * Returns a hash code for this enum constant.
136: *
137: * @return a hash code for this enum constant.
138: */
139: public final int hashCode() {
140: return super .hashCode();
141: }
142:
143: /**
144: * Throws CloneNotSupportedException. This guarantees that enums
145: * are never cloned, which is necessary to preserve their "singleton"
146: * status.
147: *
148: * @return (never returns)
149: */
150: protected final Object clone() throws CloneNotSupportedException {
151: throw new CloneNotSupportedException();
152: }
153:
154: /**
155: * Compares this enum with the specified object for order. Returns a
156: * negative integer, zero, or a positive integer as this object is less
157: * than, equal to, or greater than the specified object.
158: *
159: * Enum constants are only comparable to other enum constants of the
160: * same enum type. The natural order implemented by this
161: * method is the order in which the constants are declared.
162: */
163: public final int compareTo(E o) {
164: Enum other = (Enum) o;
165: Enum self = this ;
166: if (self.getClass() != other.getClass() && // optimization
167: self.getDeclaringClass() != other.getDeclaringClass())
168: throw new ClassCastException();
169: return self.ordinal - other.ordinal;
170: }
171:
172: /**
173: * Returns the Class object corresponding to this enum constant's
174: * enum type. Two enum constants e1 and e2 are of the
175: * same enum type if and only if
176: * e1.getDeclaringClass() == e2.getDeclaringClass().
177: * (The value returned by this method may differ from the one returned
178: * by the {@link Object#getClass} method for enum constants with
179: * constant-specific class bodies.)
180: *
181: * @return the Class object corresponding to this enum constant's
182: * enum type
183: */
184: public final Class<E> getDeclaringClass() {
185: Class clazz = getClass();
186: Class zuper = clazz.getSuperclass();
187: return (zuper == Enum.class) ? clazz : zuper;
188: }
189:
190: /**
191: * Returns the enum constant of the specified enum type with the
192: * specified name. The name must match exactly an identifier used
193: * to declare an enum constant in this type. (Extraneous whitespace
194: * characters are not permitted.)
195: *
196: * @param enumType the {@code Class} object of the enum type from which
197: * to return a constant
198: * @param name the name of the constant to return
199: * @return the enum constant of the specified enum type with the
200: * specified name
201: * @throws IllegalArgumentException if the specified enum type has
202: * no constant with the specified name, or the specified
203: * class object does not represent an enum type
204: * @throws NullPointerException if {@code enumType} or {@code name}
205: * is null
206: * @since 1.5
207: */
208: public static <T extends Enum<T>> T valueOf(Class<T> enumType,
209: String name) {
210: T result = enumType.enumConstantDirectory().get(name);
211: if (result != null)
212: return result;
213: if (name == null)
214: throw new NullPointerException("Name is null");
215: throw new IllegalArgumentException("No enum const " + enumType
216: + "." + name);
217: }
218:
219: /**
220: * enum classes cannot have finalize methods.
221: */
222: protected final void finalize() {
223: }
224:
225: /**
226: * prevent default deserialization
227: */
228: private void readObject(ObjectInputStream in) throws IOException,
229: ClassNotFoundException {
230: throw new InvalidObjectException("can't deserialize enum");
231: }
232:
233: private void readObjectNoData() throws ObjectStreamException {
234: throw new InvalidObjectException("can't deserialize enum");
235: }
236: }
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