J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2004 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 sun.tools.jstat; |
| 27 | |
| 28 | import java.util.*; |
| 29 | |
| 30 | |
| 31 | /** |
| 32 | * A typesafe enumeration for describing mathematical operators. |
| 33 | * |
| 34 | * @author Brian Doherty |
| 35 | * @since 1.5 |
| 36 | */ |
| 37 | public abstract class Operator { |
| 38 | |
| 39 | private static int nextOrdinal = 0; |
| 40 | private static HashMap<String, Operator> map = new HashMap<String, Operator>(); |
| 41 | |
| 42 | private final String name; |
| 43 | private final int ordinal = nextOrdinal++; |
| 44 | |
| 45 | private Operator(String name) { |
| 46 | this.name = name; |
| 47 | map.put(name, this); |
| 48 | } |
| 49 | |
| 50 | protected abstract double eval(double x, double y); |
| 51 | |
| 52 | /* Operator '+' */ |
| 53 | public static final Operator PLUS = new Operator("+") { |
| 54 | protected double eval(double x, double y) { |
| 55 | return x + y; |
| 56 | } |
| 57 | }; |
| 58 | |
| 59 | /* Operator '-' */ |
| 60 | public static final Operator MINUS = new Operator("-") { |
| 61 | protected double eval(double x, double y) { |
| 62 | return x - y; |
| 63 | } |
| 64 | }; |
| 65 | |
| 66 | /* Operator '/' */ |
| 67 | public static final Operator DIVIDE = new Operator("/") { |
| 68 | protected double eval(double x, double y) { |
| 69 | if (y == 0) { |
| 70 | return Double.NaN; |
| 71 | } |
| 72 | return x / y; |
| 73 | } |
| 74 | }; |
| 75 | |
| 76 | /* Operator '*' */ |
| 77 | public static final Operator MULTIPLY = new Operator("*") { |
| 78 | protected double eval(double x, double y) { |
| 79 | return x * y; |
| 80 | } |
| 81 | }; |
| 82 | |
| 83 | /** |
| 84 | * Returns the string representation of this Operator object. |
| 85 | * |
| 86 | * @return the string representation of this Operator object |
| 87 | */ |
| 88 | public String toString() { |
| 89 | return name; |
| 90 | } |
| 91 | |
| 92 | /** |
| 93 | * Maps a string to its corresponding Operator object. |
| 94 | * |
| 95 | * @param s an string to match against Operator objects. |
| 96 | * @return The Operator object matching the given string. |
| 97 | */ |
| 98 | public static Operator toOperator(String s) { |
| 99 | return map.get(s); |
| 100 | } |
| 101 | |
| 102 | /** |
| 103 | * Returns an enumeration of the keys for this enumerated type |
| 104 | * |
| 105 | * @param s an string to match against Operator objects. |
| 106 | * @return The Operator object matching the given string. |
| 107 | */ |
| 108 | protected static Set keySet() { |
| 109 | return map.keySet(); |
| 110 | } |
| 111 | } |