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1: /* Enum.java - Base class for all enums 2: Copyright (C) 2004, 2005 Free Software Foundation 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: package java.lang; 39: 40: import java.io.Serializable; 41: import java.lang.reflect.Field; 42: 43: /** 44: * This class represents a Java enumeration. All enumerations are 45: * subclasses of this class. 46: * 47: * @author Tom Tromey (tromey@redhat.com) 48: * @author Andrew John Hughes (gnu_andrew@member.fsf.org) 49: * @since 1.5 50: */ 51: public abstract class Enum<T extends Enum<T>> 52: implements Comparable<T>, Serializable 53: { 54: 55: /** 56: * For compatability with Sun's JDK 57: */ 58: private static final long serialVersionUID = -4300926546619394005L; 59: 60: /** 61: * The name of this enum constant. 62: */ 63: final String name; 64: 65: /** 66: * The number of this enum constant. Each constant is given a number 67: * which matches the order in which it was declared, starting with zero. 68: */ 69: final int ordinal; 70: 71: /** 72: * This constructor is used by the compiler to create enumeration constants. 73: * 74: * @param name the name of the enumeration constant. 75: * @param ordinal the number of the enumeration constant, based on the 76: * declaration order of the constants and starting from zero. 77: */ 78: protected Enum(String name, int ordinal) 79: { 80: this.name = name; 81: this.ordinal = ordinal; 82: } 83: 84: /** 85: * Returns an Enum for a enum class given a description string of 86: * the enum constant. 87: * 88: * @exception NullPointerException when etype or s are null. 89: * @exception IllegalArgumentException when there is no value s in 90: * the enum etype. 91: */ 92: public static <S extends Enum<S>> S valueOf(Class<S> etype, String s) 93: { 94: if (etype == null || s == null) 95: throw new NullPointerException(); 96: 97: try 98: { 99: // XXX We should not use getDeclaredField, because it does 100: // an unnecessary security check. 101: Field f = etype.getDeclaredField(s); 102: if (! f.isEnumConstant()) 103: throw new IllegalArgumentException(s); 104: Class.setAccessible(f); 105: @SuppressWarnings("unchecked") 106: S val = (S) f.get(null); 107: return val; 108: } 109: catch (NoSuchFieldException exception) 110: { 111: throw new IllegalArgumentException(s); 112: } 113: catch (IllegalAccessException exception) 114: { 115: throw new Error("Unable to access Enum class"); 116: } 117: } 118: 119: /** 120: * Returns true if this enumeration is equivalent to the supplied object, 121: * <code>o</code>. Only one instance of an enumeration constant exists, 122: * so the comparison is simply done using <code>==</code>. 123: * 124: * @param o the object to compare to this. 125: * @return true if <code>this == o</code>. 126: */ 127: public final boolean equals(Object o) 128: { 129: // Enum constants are singular, so we need only compare `=='. 130: return this == o; 131: } 132: 133: /** 134: * Returns the hash code of this constant. This is simply the ordinal. 135: * 136: * @return the hash code of this enumeration constant. 137: */ 138: public final int hashCode() 139: { 140: return ordinal; 141: } 142: 143: /** 144: * Returns a textual representation of this enumeration constant. 145: * By default, this is simply the declared name of the constant, but 146: * specific enumeration types may provide an implementation more suited 147: * to the data being stored. 148: * 149: * @return a textual representation of this constant. 150: */ 151: public String toString() 152: { 153: return name; 154: } 155: 156: /** 157: * Returns an integer which represents the relative ordering of this 158: * enumeration constant. Enumeration constants are ordered by their 159: * ordinals, which represents their declaration order. So, comparing 160: * two identical constants yields zero, while one declared prior to 161: * this returns a positive integer and one declared after yields a 162: * negative integer. 163: * 164: * @param e the enumeration constant to compare. 165: * @return a negative integer if <code>e.ordinal < this.ordinal</code>, 166: * zero if <code>e.ordinal == this.ordinal</code> and a positive 167: * integer if <code>e.ordinal > this.ordinal</code>. 168: * @throws ClassCastException if <code>e</code> is not an enumeration 169: * constant of the same class. 170: */ 171: public final int compareTo(T e) 172: { 173: if (getDeclaringClass() != e.getDeclaringClass()) 174: throw new ClassCastException(); 175: return ordinal - e.ordinal; 176: } 177: 178: /** 179: * Cloning of enumeration constants is prevented, to maintain their 180: * singleton status. 181: * 182: * @return the cloned object. 183: * @throws CloneNotSupportedException as enumeration constants can't be 184: * cloned. 185: */ 186: protected final Object clone() throws CloneNotSupportedException 187: { 188: throw new CloneNotSupportedException("can't clone an enum constant"); 189: } 190: 191: /** 192: * Returns the name of this enumeration constant. 193: * 194: * @return the name of the constant. 195: */ 196: public final String name() 197: { 198: return name; 199: } 200: 201: /** 202: * Returns the number of this enumeration constant, which represents 203: * the order in which it was originally declared, starting from zero. 204: * 205: * @return the number of this constant. 206: */ 207: public final int ordinal() 208: { 209: return ordinal; 210: } 211: 212: /** 213: * Returns the type of this enumeration constant. This is the class 214: * corresponding to the declaration of the enumeration. 215: * 216: * @return the type of this enumeration constant. 217: */ 218: public final Class<T> getDeclaringClass() 219: { 220: Class k = getClass(); 221: // We might be in an anonymous subclass of the enum class, so go 222: // up one more level. 223: if (k.getSuperclass() != Enum.class) 224: k = k.getSuperclass(); 225: return k; 226: } 227: 228: /** 229: * Enumerations can not have finalization methods. 230: * 231: * @since 1.6 232: */ 233: protected final void finalize() 234: { 235: } 236: 237: }