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1: /* EnumSyntax.java -- 2: Copyright (C) 2003, 2005 Free Software Foundation, Inc. 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 javax.print.attribute; 39: 40: import java.io.InvalidObjectException; 41: import java.io.ObjectStreamException; 42: import java.io.Serializable; 43: 44: /** 45: * <code>EnumSyntax</code> is the abstract base class of all enumeration 46: * classes in the Java Print Service API. 47: * <p> 48: * Every enumeration class which extends from EnumSyntax provides several 49: * enumeration objects as singletons of its class. 50: * </p> 51: * <p> 52: * Notes for implementing subclasses: 53: * <ul> 54: * <li> 55: * The values of all enumeration singelton instances have to be in a 56: * sequence which may start at any value. See: {@link #getOffset()} 57: * </li> 58: * <li> 59: * Subclasses have to override {@link #getEnumValueTable()} and should 60: * override {@link #getStringTable()} for correct serialization. 61: * </li> 62: * </ul> 63: * </p> 64: * Example: 65: * <pre> 66: * public class PrinterState extends EnumSyntax 67: * { 68: * public static final PrinterState IDLE = new PrinterState(1); 69: * public static final PrinterState PROCESSING = new PrinterState(2); 70: * public static final PrinterState STOPPED = new PrinterState(3); 71: * 72: * protected PrinterState(int value) 73: * { 74: * super(value); 75: * } 76: * 77: * // Overridden because values start not at zero ! 78: * protected int getOffset() 79: * { 80: * return 1; 81: * } 82: * 83: * private static final String[] stringTable = { "idle", "processing", 84: * "stopped" }; 85: * 86: * protected String[] getStringTable() 87: * { 88: * return stringTable; 89: * } 90: * 91: * private static final PrinterState[] enumValueTable = { IDLE, 92: * PROCESSING, STOPPED}; 93: * 94: * protected EnumSyntax[] getEnumValueTable() 95: * { 96: * return enumValueTable; 97: * } 98: * } 99: * </pre> 100: * 101: * @author Michael Koch (konqueror@gmx.de) 102: * @author Wolfgang Baer (WBaer@gmx.de) 103: */ 104: public abstract class EnumSyntax implements Cloneable, Serializable 105: { 106: private static final long serialVersionUID = -2739521845085831642L; 107: 108: private int value; 109: 110: /** 111: * Creates a <code>EnumSyntax</code> object. 112: * 113: * @param value the value to set. 114: */ 115: protected EnumSyntax(int value) 116: { 117: this.value = value; 118: } 119: 120: /** 121: * Returns the value of this enumeration object. 122: * 123: * @return The value. 124: */ 125: public int getValue() 126: { 127: return value; 128: } 129: 130: /** 131: * Clones this object. 132: * 133: * @return A clone of this object. 134: */ 135: public Object clone() 136: { 137: try 138: { 139: return super.clone(); 140: } 141: catch (CloneNotSupportedException e) 142: { 143: // Cannot happen as we implement java.lang.Cloneable. 144: return null; 145: } 146: } 147: 148: /** 149: * Returns the hashcode for this object. 150: * The hashcode is the value of this enumeration object. 151: * 152: * @return The hashcode. 153: */ 154: public int hashCode() 155: { 156: return value; 157: } 158: 159: /** 160: * Returns the string representation for this object. 161: * The string value from <code>getStringTable()</code> method is returned 162: * if subclasses override this method. Otherwise the value of this object 163: * as a string is returned. 164: * 165: * @return The string representation. 166: */ 167: public String toString() 168: { 169: int index = value - getOffset(); 170: String[] table = getStringTable(); 171: 172: if (table != null 173: && index >= 0 174: && index < table.length) 175: return table[index]; 176: 177: return "" + value; 178: } 179: 180: /** 181: * Returns a table with the enumeration values represented as strings 182: * for this object. 183: * 184: * The default implementation just returns null. Subclasses should 185: * override this method. 186: * 187: * @return The enumeration values as strings. 188: */ 189: protected String[] getStringTable() 190: { 191: return null; 192: } 193: 194: /** 195: * Needed for singelton semantics during deserialisation. 196: * 197: * Subclasses must not override this class. Subclasses have to override 198: * <code>getEnumValueTable()</code> and should override 199: * <code>getStringTable()</code> for correct serialization. 200: * 201: * @return The Object at index <code>value - getOffset()</code> 202: * in getEnumValueTable. 203: * @throws ObjectStreamException if getEnumValueTable() returns null. 204: */ 205: protected Object readResolve() throws ObjectStreamException 206: { 207: EnumSyntax[] table = getEnumValueTable(); 208: if (table == null) 209: throw new InvalidObjectException("Null enumeration value table " 210: + "for class " 211: + this.getClass().toString()); 212: 213: return table[value - getOffset()]; 214: } 215: 216: /** 217: * Returns a table with the enumeration values for this object. 218: * 219: * The default implementation just returns null. Subclasses have to 220: * to override this method for serialization. 221: * 222: * @return The enumeration values. 223: */ 224: protected EnumSyntax[] getEnumValueTable() 225: { 226: return null; 227: } 228: 229: /** 230: * Returns the lowest used value by the enumerations of this class. 231: * 232: * The default implementation returns 0. This is enough if enumerations 233: * start with a zero value. Otherwise subclasses need to override this 234: * method for serialization and return the lowest value they use. 235: * . 236: * @return The lowest used value used. 237: */ 238: protected int getOffset() 239: { 240: return 0; 241: } 242: }