Frames | No Frames |
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: /* FIXME[GENERICS]: Should be Enum<T extends Enum<T>> 52: and Comparable<T> */ 53: public abstract class Enum 54: implements Comparable, Serializable 55: { 56: 57: /** 58: * For compatability with Sun's JDK 59: */ 60: private static final long serialVersionUID = -4300926546619394005L; 61: 62: /** 63: * The name of this enum constant. 64: */ 65: String name; 66: 67: /** 68: * The number of this enum constant. Each constant is given a number 69: * which matches the order in which it was declared, starting with zero. 70: */ 71: int ordinal; 72: 73: /** 74: * This constructor is used by the compiler to create enumeration constants. 75: * 76: * @param name the name of the enumeration constant. 77: * @param ordinal the number of the enumeration constant, based on the 78: * declaration order of the constants and starting from zero. 79: */ 80: protected Enum(String name, int ordinal) 81: { 82: this.name = name; 83: this.ordinal = ordinal; 84: } 85: 86: /** 87: * Returns an Enum for a enum class given a description string of 88: * the enum constant. 89: * 90: * @exception NullPointerException when etype or s are null. 91: * @exception IllegalArgumentException when there is no value s in 92: * the enum etype. 93: */ 94: /* FIXME[GENERICS]: Should be <S extends Enum<S>> S valueOf(Class<S>) */ 95: public static Enum valueOf(Class etype, String s) 96: { 97: if (etype == null || s == null) 98: throw new NullPointerException(); 99: 100: try 101: { 102: Field f = etype.getDeclaredField(s); 103: if (! f.isEnumConstant()) 104: throw new IllegalArgumentException(s); 105: /* FIXME[GENERICS]: Should cast to S */ 106: return (Enum) f.get(null); 107: } 108: catch (NoSuchFieldException exception) 109: { 110: throw new IllegalArgumentException(s); 111: } 112: catch (IllegalAccessException exception) 113: { 114: throw new Error("Unable to access Enum class"); 115: } 116: } 117: 118: /** 119: * Returns true if this enumeration is equivalent to the supplied object, 120: * <code>o</code>. Only one instance of an enumeration constant exists, 121: * so the comparison is simply done using <code>==</code>. 122: * 123: * @param o the object to compare to this. 124: * @return true if <code>this == o</code>. 125: */ 126: public final boolean equals(Object o) 127: { 128: // Enum constants are singular, so we need only compare `=='. 129: return this == o; 130: } 131: 132: /** 133: * Returns the hash code of this constant. This is simply the ordinal. 134: * 135: * @return the hash code of this enumeration constant. 136: */ 137: public final int hashCode() 138: { 139: return ordinal; 140: } 141: 142: /** 143: * Returns a textual representation of this enumeration constant. 144: * By default, this is simply the declared name of the constant, but 145: * specific enumeration types may provide an implementation more suited 146: * to the data being stored. 147: * 148: * @return a textual representation of this constant. 149: */ 150: public String toString() 151: { 152: return name; 153: } 154: 155: /** 156: * Returns an integer which represents the relative ordering of this 157: * enumeration constant. Enumeration constants are ordered by their 158: * ordinals, which represents their declaration order. So, comparing 159: * two identical constants yields zero, while one declared prior to 160: * this returns a positive integer and one declared after yields a 161: * negative integer. 162: * 163: * @param e the enumeration constant to compare. 164: * @return a negative integer if <code>e.ordinal < this.ordinal</code>, 165: * zero if <code>e.ordinal == this.ordinal</code> and a positive 166: * integer if <code>e.ordinal > this.ordinal</code>. 167: * @throws ClassCastException if <code>e</code> is not an enumeration 168: * constant of the same class. 169: */ 170: public final int compareTo(Enum e) 171: { 172: if (getDeclaringClass() != e.getDeclaringClass()) 173: throw new ClassCastException(); 174: return ordinal - e.ordinal; 175: } 176: 177: /** 178: * Returns an integer which represents the relative ordering of this 179: * enumeration constant. Enumeration constants are ordered by their 180: * ordinals, which represents their declaration order. So, comparing 181: * two identical constants yields zero, while one declared prior to 182: * this returns a positive integer and one declared after yields a 183: * negative integer. 184: * 185: * @param o the enumeration constant to compare. 186: * @return a negative integer if <code>e.ordinal < this.ordinal</code>, 187: * zero if <code>e.ordinal == this.ordinal</code> and a positive 188: * integer if <code>e.ordinal > this.ordinal</code>. 189: * @throws ClassCastException if <code>e</code> is not an enumeration 190: * constant of the same class. 191: */ 192: /* FIXME[GENERICS]: Remove this method */ 193: public final int compareTo(Object o) 194: { 195: return compareTo((Enum)o); 196: } 197: 198: /** 199: * Cloning of enumeration constants is prevented, to maintain their 200: * singleton status. 201: * 202: * @return the cloned object. 203: * @throws CloneNotSupportedException as enumeration constants can't be 204: * cloned. 205: */ 206: protected final Object clone() throws CloneNotSupportedException 207: { 208: throw new CloneNotSupportedException("can't clone an enum constant"); 209: } 210: 211: /** 212: * Returns the name of this enumeration constant. 213: * 214: * @return the name of the constant. 215: */ 216: public final String name() 217: { 218: return name; 219: } 220: 221: /** 222: * Returns the number of this enumeration constant, which represents 223: * the order in which it was originally declared, starting from zero. 224: * 225: * @return the number of this constant. 226: */ 227: public final int ordinal() 228: { 229: return ordinal; 230: } 231: 232: /** 233: * Returns the type of this enumeration constant. This is the class 234: * corresponding to the declaration of the enumeration. 235: * 236: * @return the type of this enumeration constant. 237: */ 238: /* FIXME[GENERICS]: Should return Class<T> */ 239: public final Class getDeclaringClass() 240: { 241: Class k = getClass(); 242: // We might be in an anonymous subclass of the enum class, so go 243: // up one more level. 244: if (k.getSuperclass() != Enum.class) 245: k = k.getSuperclass(); 246: return k; 247: } 248: }