Java tutorial
/* =========================================================== * JFreeChart : a free chart library for the Java(tm) platform * =========================================================== * * (C) Copyright 2000-2013, by Object Refinery Limited and Contributors. * * Project Info: http://www.jfree.org/jfreechart/index.html * * This library is free software; you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation; either version 2.1 of the License, or * (at your option) any later version. * * This library 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 Lesser General Public * License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, * USA. * * [Oracle and Java are registered trademarks of Oracle and/or its affiliates. * Other names may be trademarks of their respective owners.] * * --------------- * XYDataItem.java * --------------- * (C) Copyright 2003-2013, by Object Refinery Limited. * * Original Author: David Gilbert (for Object Refinery Limited); * Contributor(s): -; * * Changes * ------- * 05-Aug-2003 : Renamed XYDataPair --> XYDataItem (DG); * 03-Feb-2004 : Fixed bug in equals() method (DG); * 21-Feb-2005 : Added setY(double) method (DG); * ------------- JFREECHART 1.0.x --------------------------------------------- * 30-Nov-2007 : Implemented getXValue() and getYValue(), plus toString() for * debugging use (DG); * 10-Jun-2009 : Reimplemented cloning (DG); * 02-Jul-2013 : Use ParamChecks (DG); * */ package org.jfree.data.xy; import java.io.Serializable; import org.jfree.chart.util.ParamChecks; import org.jfree.util.ObjectUtilities; /** * Represents one (x, y) data item for an {@link XYSeries}. Note that * subclasses are REQUIRED to support cloning. */ public class XYDataItem implements Cloneable, Comparable, Serializable { /** For serialization. */ private static final long serialVersionUID = 2751513470325494890L; /** The x-value (<code>null</code> not permitted). */ private Number x; /** The y-value. */ private Number y; /** * Constructs a new data item. * * @param x the x-value (<code>null</code> NOT permitted). * @param y the y-value (<code>null</code> permitted). */ public XYDataItem(Number x, Number y) { ParamChecks.nullNotPermitted(x, "x"); this.x = x; this.y = y; } /** * Constructs a new data item. * * @param x the x-value. * @param y the y-value. */ public XYDataItem(double x, double y) { this(new Double(x), new Double(y)); } /** * Returns the x-value. * * @return The x-value (never <code>null</code>). */ public Number getX() { return this.x; } /** * Returns the x-value as a double primitive. * * @return The x-value. * * @see #getX() * @see #getYValue() * * @since 1.0.9 */ public double getXValue() { // this.x is not allowed to be null... return this.x.doubleValue(); } /** * Returns the y-value. * * @return The y-value (possibly <code>null</code>). */ public Number getY() { return this.y; } /** * Returns the y-value as a double primitive. * * @return The y-value. * * @see #getY() * @see #getXValue() * * @since 1.0.9 */ public double getYValue() { double result = Double.NaN; if (this.y != null) { result = this.y.doubleValue(); } return result; } /** * Sets the y-value for this data item. Note that there is no * corresponding method to change the x-value. * * @param y the new y-value. */ public void setY(double y) { setY(new Double(y)); } /** * Sets the y-value for this data item. Note that there is no * corresponding method to change the x-value. * * @param y the new y-value (<code>null</code> permitted). */ public void setY(Number y) { this.y = y; } /** * Returns an integer indicating the order of this object relative to * another object. * <P> * For the order we consider only the x-value: * negative == "less-than", zero == "equal", positive == "greater-than". * * @param o1 the object being compared to. * * @return An integer indicating the order of this data pair object * relative to another object. */ @Override public int compareTo(Object o1) { int result; // CASE 1 : Comparing to another TimeSeriesDataPair object // ------------------------------------------------------- if (o1 instanceof XYDataItem) { XYDataItem dataItem = (XYDataItem) o1; double compare = this.x.doubleValue() - dataItem.getX().doubleValue(); if (compare > 0.0) { result = 1; } else { if (compare < 0.0) { result = -1; } else { result = 0; } } } // CASE 2 : Comparing to a general object // --------------------------------------------- else { // consider time periods to be ordered after general objects result = 1; } return result; } /** * Returns a clone of this object. * * @return A clone. */ @Override public Object clone() { Object clone = null; try { clone = super.clone(); } catch (CloneNotSupportedException e) { // won't get here... e.printStackTrace(); } return clone; } /** * Tests if this object is equal to another. * * @param obj the object to test against for equality (<code>null</code> * permitted). * * @return A boolean. */ @Override public boolean equals(Object obj) { if (obj == this) { return true; } if (!(obj instanceof XYDataItem)) { return false; } XYDataItem that = (XYDataItem) obj; if (!this.x.equals(that.x)) { return false; } if (!ObjectUtilities.equal(this.y, that.y)) { return false; } return true; } /** * Returns a hash code. * * @return A hash code. */ @Override public int hashCode() { int result; result = this.x.hashCode(); result = 29 * result + (this.y != null ? this.y.hashCode() : 0); return result; } /** * Returns a string representing this instance, primarily for debugging * use. * * @return A string. */ @Override public String toString() { return "[" + getXValue() + ", " + getYValue() + "]"; } }