1 /* 2 * Copyright (c) 2004, Oracle and/or its affiliates. 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. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * 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 Operator(String name)45 private Operator(String name) { 46 this.name = name; 47 map.put(name, this); 48 } 49 eval(double x, double y)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 */ toString()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 */ toOperator(String s)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 */ keySet()108 protected static Set<?> keySet() { 109 return map.keySet(); 110 } 111 } 112