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}