    001/* ===========================================================
    002 * JFreeChart : a free chart library for the Java(tm) platform
    003 * ===========================================================
    004 *
    005 * (C) Copyright 2000-2011, by Object Refinery Limited and Contributors.
    006 *
    007 * Project Info:  http://www.jfree.org/jfreechart/index.html
    008 *
    009 * This library is free software; you can redistribute it and/or modify it
    010 * under the terms of the GNU Lesser General Public License as published by
    011 * the Free Software Foundation; either version 2.1 of the License, or
    012 * (at your option) any later version.
    013 *
    014 * This library is distributed in the hope that it will be useful, but
    015 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    016 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
    017 * License for more details.
    018 *
    019 * You should have received a copy of the GNU Lesser General Public
    020 * License along with this library; if not, write to the Free Software
    021 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
    022 * USA.
    023 *
    024 * [Oracle and Java are registered trademarks of Oracle and/or its affiliates.
    025 * Other names may be trademarks of their respective owners.]
    026 *
    027 * -------------------
    028 * LineFunction2D.java
    029 * -------------------
    030 * (C) Copyright 2002-2009, by Object Refinery Limited.
    031 *
    032 * Original Author:  David Gilbert (for Object Refinery Limited);
    033 * Contributor(s):   -;
    034 *
    035 * Changes:
    036 * --------
    037 * 01-Oct-2002 : Version 1 (DG);
    038 * 28-May-2009 : Added accessor methods for co-efficients, implemented
    039 *               equals() and hashCode(), and added Serialization support (DG);
    040 *
    041 */
    042
    043package org.jfree.data.function;
    044
    045import java.io.Serializable;
    046
    047import org.jfree.chart.HashUtilities;
    048
    049/**
    050 * A function in the form y = a + bx.
    051 */
    052public class LineFunction2D implements Function2D, Serializable {
    053
    054    /** The intercept. */
    055    private double a;
    056
    057    /** The slope of the line. */
    058    private double b;
    059
    060    /**
    061     * Constructs a new line function.
    062     *
    063     * @param a  the intercept.
    064     * @param b  the slope.
    065     */
    066    public LineFunction2D(double a, double b) {
    067        this.a = a;
    068        this.b = b;
    069    }
    070
    071    /**
    072     * Returns the 'a' coefficient that was specified in the constructor.
    073     *
    074     * @return The 'a' coefficient.
    075     *
    076     * @since 1.0.14
    077     */
    078    public double getIntercept() {
    079        return this.a;
    080    }
    081
    082    /**
    083     * Returns the 'b' coefficient that was specified in the constructor.
    084     *
    085     * @return The 'b' coefficient.
    086     *
    087     * @since 1.0.14
    088     */
    089    public double getSlope() {
    090        return this.b;
    091    }
    092
    093    /**
    094     * Returns the function value.
    095     *
    096     * @param x  the x-value.
    097     *
    098     * @return The value.
    099     */
    100    public double getValue(double x) {
    101        return this.a + this.b * x;
    102    }
    103
    104    /**
    105     * Tests this function for equality with an arbitrary object.
    106     *
    107     * @param obj  the object (<code>null</code> permitted).
    108     *
    109     * @return A boolean.
    110     */
    111    public boolean equals(Object obj) {
    112        if (!(obj instanceof LineFunction2D)) {
    113            return false;
    114        }
    115        LineFunction2D that = (LineFunction2D) obj;
    116        if (this.a != that.a) {
    117            return false;
    118        }
    119        if (this.b != that.b) {
    120            return false;
    121        }
    122        return true;
    123    }
    124
    125    /**
    126     * Returns a hash code for this instance.
    127     *
    128     * @return A hash code.
    129     */
    130    public int hashCode() {
    131        int result = 29;
    132        result = HashUtilities.hashCode(result, this.a);
    133        result = HashUtilities.hashCode(result, this.b);
    134        return result;
    135    }
    136}