001/* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-2022, by David Gilbert 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 2002-2022, by David Gilbert.
031 *
032 * Original Author:  David Gilbert;
033 * Contributor(s):   -;
034 *
035 */
036
037package org.jfree.data.function;
038
039import java.io.Serializable;
040
041import org.jfree.chart.internal.HashUtils;
042
043/**
044 * A function in the form y = a + bx.
045 */
046public class LineFunction2D implements Function2D, Serializable {
047
048    /** The intercept. */
049    private double a;
050
051    /** The slope of the line. */
052    private double b;
053
054    /**
055     * Constructs a new line function.
056     *
057     * @param a  the intercept.
058     * @param b  the slope.
059     */
060    public LineFunction2D(double a, double b) {
061        this.a = a;
062        this.b = b;
063    }
064
065    /**
066     * Returns the 'a' coefficient that was specified in the constructor.
067     *
068     * @return The 'a' coefficient.
069     *
070     * @since 1.0.14
071     */
072    public double getIntercept() {
073        return this.a;
074    }
075
076    /**
077     * Returns the 'b' coefficient that was specified in the constructor.
078     *
079     * @return The 'b' coefficient.
080     *
081     * @since 1.0.14
082     */
083    public double getSlope() {
084        return this.b;
085    }
086
087    /**
088     * Returns the function value.
089     *
090     * @param x  the x-value.
091     *
092     * @return The value.
093     */
094    @Override
095    public double getValue(double x) {
096        return this.a + this.b * x;
097    }
098
099    /**
100     * Tests this function for equality with an arbitrary object.
101     *
102     * @param obj  the object ({@code null} permitted).
103     *
104     * @return A boolean.
105     */
106    @Override
107    public boolean equals(Object obj) {
108        if (!(obj instanceof LineFunction2D)) {
109            return false;
110        }
111        LineFunction2D that = (LineFunction2D) obj;
112        if (this.a != that.a) {
113            return false;
114        }
115        if (this.b != that.b) {
116            return false;
117        }
118        return true;
119    }
120
121    /**
122     * Returns a hash code for this instance.
123     * 
124     * @return A hash code.
125     */
126    @Override
127    public int hashCode() {
128        int result = 29;
129        result = HashUtils.hashCode(result, this.a);
130        result = HashUtils.hashCode(result, this.b);
131        return result;
132    }
133}