Operation.java revision 3233:b5d08bc0d224 
1/*
2 * Copyright (c) 2003, 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.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24package pkg1;
25
26/*
27 * Example from JSR 201, which borrowed it from "Effective Java".
28 */
29
30/**
31 * Arithmetic operations.
32 */
33public abstract enum Operation {
34    /** Addition */
35    plus {
36        /** Add 'em up. */
37        double eval(double x, double y) { return x + y; }
38    },
39    minus {
40        double eval(double x, double y) { return x - y; }
41    },
42    times {
43        double eval(double x, double y) { return x * y; }
44    },
45    divided_by {
46        double eval(double x, double y) { return x / y; }
47    };
48
49    /**
50     * Perform arithmetic operation represented by this constant.
51     */
52    abstract double eval(double x, double y);
53}
54