Operation.java

/*
 * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package pkg1;

/*
 * Example from JSR 201, which borrowed it from "Effective Java".
 */

/**
 * Arithmetic operations.
 */
public enum Operation {
    /** Addition */
    plus {
        /** Add 'em up. */
        double eval(double x, double y) { return x + y; }
    },
    minus {
        double eval(double x, double y) { return x - y; }
    },
    times {
        double eval(double x, double y) { return x * y; }
    },
    divided_by {
        double eval(double x, double y) { return x / y; }
    };

    /**
     * Perform arithmetic operation represented by this constant.
     */
    abstract double eval(double x, double y);
}