1 /* 2 * Copyright 2003-2007 Sun Microsystems, Inc. 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. Sun designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 22 * CA 95054 USA or visit www.sun.com if you need additional information or 23 * have any 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 * @author Josh Bloch 38 * @author Neal Gafter 39 * @see Class#getEnumConstants() 40 * @since 1.5 41 */ 42 public abstract class Enum<E extends Enum<E>> 43 implements Comparable<E>, Serializable { 44 /** 45 * The name of this enum constant, as declared in the enum declaration. 46 * Most programmers should use the {@link #toString} method rather than 47 * accessing this field. 48 */ 49 private final String name; 50 51 /** 52 * Returns the name of this enum constant, exactly as declared in its 53 * enum declaration. 54 * 55 * <b>Most programmers should use the {@link #toString} method in 56 * preference to this one, as the toString method may return 57 * a more user-friendly name.</b> This method is designed primarily for 58 * use in specialized situations where correctness depends on getting the 59 * exact name, which will not vary from release to release. 60 * 61 * @return the name of this enum constant 62 */ 63 public final String name() { 64 return name; 65 } 66 67 /** 68 * The ordinal of this enumeration constant (its position 69 * in the enum declaration, where the initial constant is assigned 70 * an ordinal of zero). 71 * 72 * Most programmers will have no use for this field. It is designed 73 * for use by sophisticated enum-based data structures, such as 74 * {@link java.util.EnumSet} and {@link java.util.EnumMap}. 75 */ 76 private final int ordinal; 77 78 /** 79 * Returns the ordinal of this enumeration constant (its position 80 * in its enum declaration, where the initial constant is assigned 81 * an ordinal of zero). 82 * 83 * Most programmers will have no use for this method. It is 84 * designed for use by sophisticated enum-based data structures, such 85 * as {@link java.util.EnumSet} and {@link java.util.EnumMap}. 86 * 87 * @return the ordinal of this enumeration constant 88 */ 89 public final int ordinal() { 90 return ordinal; 91 } 92 93 /** 94 * Sole constructor. Programmers cannot invoke this constructor. 95 * It is for use by code emitted by the compiler in response to 96 * enum type declarations. 97 * 98 * @param name - The name of this enum constant, which is the identifier 99 * used to declare it. 100 * @param ordinal - The ordinal of this enumeration constant (its position 101 * in the enum declaration, where the initial constant is assigned 102 * an ordinal of zero). 103 */ 104 protected Enum(String name, int ordinal) { 105 this.name = name; 106 this.ordinal = ordinal; 107 } 108 109 /** 110 * Returns the name of this enum constant, as contained in the 111 * declaration. This method may be overridden, though it typically 112 * isn't necessary or desirable. An enum type should override this 113 * method when a more "programmer-friendly" string form exists. 114 * 115 * @return the name of this enum constant 116 */ 117 public String toString() { 118 return name; 119 } 120 121 /** 122 * Returns true if the specified object is equal to this 123 * enum constant. 124 * 125 * @param other the object to be compared for equality with this object. 126 * @return true if the specified object is equal to this 127 * enum constant. 128 */ 129 public final boolean equals(Object other) { 130 return this==other; 131 } 132 133 /** 134 * Returns a hash code for this enum constant. 135 * 136 * @return a hash code for this enum constant. 137 */ 138 public final int hashCode() { 139 return super.hashCode(); 140 } 141 142 /** 143 * Throws CloneNotSupportedException. This guarantees that enums 144 * are never cloned, which is necessary to preserve their "singleton" 145 * status. 146 * 147 * @return (never returns) 148 */ 149 protected final Object clone() throws CloneNotSupportedException { 150 throw new CloneNotSupportedException(); 151 } 152 153 /** 154 * Compares this enum with the specified object for order. Returns a 155 * negative integer, zero, or a positive integer as this object is less 156 * than, equal to, or greater than the specified object. 157 * 158 * Enum constants are only comparable to other enum constants of the 159 * same enum type. The natural order implemented by this 160 * method is the order in which the constants are declared. 161 */ 162 public final int compareTo(E o) { 163 Enum other = (Enum)o; 164 Enum self = this; 165 if (self.getClass() != other.getClass() && // optimization 166 self.getDeclaringClass() != other.getDeclaringClass()) 167 throw new ClassCastException(); 168 return self.ordinal - other.ordinal; 169 } 170 171 /** 172 * Returns the Class object corresponding to this enum constant's 173 * enum type. Two enum constants e1 and e2 are of the 174 * same enum type if and only if 175 * e1.getDeclaringClass() == e2.getDeclaringClass(). 176 * (The value returned by this method may differ from the one returned 177 * by the {@link Object#getClass} method for enum constants with 178 * constant-specific class bodies.) 179 * 180 * @return the Class object corresponding to this enum constant's 181 * enum type 182 */ 183 public final Class<E> getDeclaringClass() { 184 Class clazz = getClass(); 185 Class zuper = clazz.getSuperclass(); 186 return (zuper == Enum.class) ? clazz : zuper; 187 } 188 189 /** 190 * Returns the enum constant of the specified enum type with the 191 * specified name. The name must match exactly an identifier used 192 * to declare an enum constant in this type. (Extraneous whitespace 193 * characters are not permitted.) 194 * 195 * @param enumType the {@code Class} object of the enum type from which 196 * to return a constant 197 * @param name the name of the constant to return 198 * @return the enum constant of the specified enum type with the 199 * specified name 200 * @throws IllegalArgumentException if the specified enum type has 201 * no constant with the specified name, or the specified 202 * class object does not represent an enum type 203 * @throws NullPointerException if {@code enumType} or {@code name} 204 * is null 205 * @since 1.5 206 */ 207 public static <T extends Enum<T>> T valueOf(Class<T> enumType, 208 String name) { 209 T result = enumType.enumConstantDirectory().get(name); 210 if (result != null) 211 return result; 212 if (name == null) 213 throw new NullPointerException("Name is null"); 214 throw new IllegalArgumentException( 215 "No enum const " + enumType +"." + name); 216 } 217 218 /** 219 * enum classes cannot have finalize methods. 220 */ 221 protected final void finalize() { } 222 223 /** 224 * prevent default deserialization 225 */ 226 private void readObject(ObjectInputStream in) throws IOException, 227 ClassNotFoundException { 228 throw new InvalidObjectException("can't deserialize enum"); 229 } 230 231 private void readObjectNoData() throws ObjectStreamException { 232 throw new InvalidObjectException("can't deserialize enum"); 233 } 234 }