在xy圖(散點圖)是根據一個數據係列組成的x和y值的列表。每個值對(x，y)是坐標係中的一個點。這裡1值確定水平(X)位置，而另一個確定垂直(Y)位置。本章演示了如何使用JFreeChart從一個給定的業務數據創建XY圖表。

業務數據

考慮這種情況，我們要創建一個XY圖表所有主要瀏覽器的一個例子。在這裡，不同的性能分數是從不同類型的人們聚集，如下所示：

Firefox	Category(X)	Score(Y)
	1.0	1.0
	2.0	4.0
	3.0	3.0

Chrome	Category(X)	Score(Y)
	1.0	4.0
	2.0	5.0
	3.0	6.0

IE	Category(X)	Score(Y)
	3.0	4.0
	4.0	5.0
	5.0	4.0

基於AWT的應用

以下是對從上述給定的信息創建XY圖表的代碼。此代碼可以在AWT應用程序嵌入一個XY圖表。

import java.awt.Color; 
import java.awt.BasicStroke; 
import org.jfree.chart.ChartPanel; 
import org.jfree.chart.JFreeChart; 
import org.jfree.data.xy.XYDataset; 
import org.jfree.data.xy.XYSeries; 
import org.jfree.ui.ApplicationFrame; 
import org.jfree.ui.RefineryUtilities; 
import org.jfree.chart.plot.XYPlot; 
import org.jfree.chart.ChartFactory; 
import org.jfree.chart.plot.PlotOrientation; 
import org.jfree.data.xy.XYSeriesCollection; 
import org.jfree.chart.renderer.xy.XYLineAndShapeRenderer;

public class XYLineChart_AWT extends ApplicationFrame 
{
   public XYLineChart_AWT( String applicationTitle, String chartTitle )
   {
      super(applicationTitle);
      JFreeChart xylineChart = ChartFactory.createXYLineChart(
         chartTitle ,
         "Category" ,
         "Score" ,
         createDataset() ,
         PlotOrientation.VERTICAL ,
         true , true , false);
         
      ChartPanel chartPanel = new ChartPanel( xylineChart );
      chartPanel.setPreferredSize( new java.awt.Dimension( 560 , 367 ) );
      final XYPlot plot = xylineChart.getXYPlot( );
      XYLineAndShapeRenderer renderer = new XYLineAndShapeRenderer( );
      renderer.setSeriesPaint( 0 , Color.RED );
      renderer.setSeriesPaint( 1 , Color.GREEN );
      renderer.setSeriesPaint( 2 , Color.YELLOW );
      renderer.setSeriesStroke( 0 , new BasicStroke( 4.0f ) );
      renderer.setSeriesStroke( 1 , new BasicStroke( 3.0f ) );
      renderer.setSeriesStroke( 2 , new BasicStroke( 2.0f ) );
      plot.setRenderer( renderer ); 
      setContentPane( chartPanel ); 
   }
   
   private XYDataset createDataset( )
   {
      final XYSeries firefox = new XYSeries( "Firefox" );          
      firefox.add( 1.0 , 1.0 );          
      firefox.add( 2.0 , 4.0 );          
      firefox.add( 3.0 , 3.0 );          
      final XYSeries chrome = new XYSeries( "Chrome" );          
      chrome.add( 1.0 , 4.0 );          
      chrome.add( 2.0 , 5.0 );          
      chrome.add( 3.0 , 6.0 );          
      final XYSeries iexplorer = new XYSeries( "InternetExplorer" );          
      iexplorer.add( 3.0 , 4.0 );          
      iexplorer.add( 4.0 , 5.0 );          
      iexplorer.add( 5.0 , 4.0 );          
      final XYSeriesCollection dataset = new XYSeriesCollection( );          
      dataset.addSeries( firefox );          
      dataset.addSeries( chrome );          
      dataset.addSeries( iexplorer );
      return dataset;
   }

   public static void main( String[ ] args ) 
   {
      XYLineChart_AWT chart = new XYLineChart_AWT("Browser Usage Statistics", "Which Browser are you using?");
      chart.pack( );          
      RefineryUtilities.centerFrameOnScreen( chart );          
      chart.setVisible( true ); 
   }
}

讓我們保存XYLineChart_AWT.java文件如上麵的Java代碼，然後從命令提示符下編譯並運行它，如下所示：

$javac XYLineChart_AWT.java 
$java XYLineChart_AWT 

如果一切順利，它會編譯並運行生成以下XY圖：

創建JPEG圖像

讓我們重新編寫上麵的例子，在命令行生成JPEG圖像。

import java.io.*;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.JFreeChart;
import org.jfree.data.xy.XYSeries;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.data.xy.XYSeriesCollection;
import org.jfree.chart.ChartUtilities; 

public class XYLineChart_image
{
   public static void main( String[ ] args )throws Exception
   {
      final XYSeries firefox = new XYSeries( "Firefox" );
      firefox.add( 1.0 , 1.0 );
      firefox.add( 2.0 , 4.0 );
      firefox.add( 3.0 , 3.0 );
      final XYSeries chrome = new XYSeries( "Chrome" );
      chrome.add( 1.0 , 4.0 );
      chrome.add( 2.0 , 5.0 );
      chrome.add( 3.0 , 6.0 );
      final XYSeries iexplorer = new XYSeries( "InternetExplorer" );
      iexplorer.add( 3.0 , 4.0 );
      iexplorer.add( 4.0 , 5.0 );
      iexplorer.add( 5.0 , 4.0 );
      final XYSeriesCollection dataset = new XYSeriesCollection( );
      dataset.addSeries( firefox );
      dataset.addSeries( chrome );
      dataset.addSeries( iexplorer );

      JFreeChart xylineChart = ChartFactory.createXYLineChart(
         "Browser usage statastics", 
         "Category",
         "Score", 
         dataset,
         PlotOrientation.VERTICAL, 
         true, true, false);
      
      int width = 640; /* Width of the image */
      int height = 480; /* Height of the image */ 
      File XYChart = new File( "XYLineChart.jpeg" ); 
      ChartUtilities.saveChartAsJPEG( XYChart, xylineChart, width, height);
   }
}

讓我們保存在XYLineChart_image.java文件如上麵的Java代碼，然後從命令提示符下編譯並運行它，如下所示：

$javac XYLineChart_image.java 
$java XYLineChart_image 

如果一切順利，它會編譯並運行在當前的目錄中創建JPEG圖像文件namedXYLineChart.jpeg。