JFreeChart - File Interface


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So far we studied how to create various types of charts using JFreeChart APIs using static data. But in production environment, data is provided in the form of text file with a predefined format, or it comes directly from the database.

This chapter will explain how we can read a simple data from a given text file from a given location and then use JFreeChart to create a chart of your choice.

Business Data

Consider we have a file named mobile.txt, having different mobile brands and their sale (units per day) separated by a simple comma (,):

Iphone 5S, 20  
Samsung Grand, 20  
MOTO G, 40  Nokia 
Lumia, 10 

Chart Generation Based on File

Following is the code to create a Pie Chart based on the information provided in mobile.txt:

import java.io.*; 
import java.util.StringTokenizer; 
import org.jfree.chart.ChartUtilities; 
import org.jfree.chart.ChartFactory; 
import org.jfree.chart.JFreeChart; 
import org.jfree.data.general.DefaultPieDataset;

public class PieChart_File 
{
   public static void main( String[ ] args )throws Exception
   {
      String mobilebrands[ ] = {    
        "IPhone 5s" ,   
        "SamSung Grand" ,   
        "MotoG" ,    
        "Nokia Lumia" 
      };
      
      InputStream in = new FileInputStream( new File( "C:/temp/test.txt" ) );          
      BufferedReader reader = new BufferedReader(new InputStreamReader(in ) );          
      StringBuilder out = new StringBuilder();          
      String line;          
      DefaultPieDataset dataset = new DefaultPieDataset();          

      while (( line = reader.readLine() ) != null ) 
      {
         out.append( line );
      }
      StringTokenizer s = new StringTokenizer( out.toString(), "," );
      int i=0;      
      while( s.hasMoreTokens( ) && ( mobilebrands [i] != null ) )
      {
         dataset.setValue(mobilebrands[i], Double.parseDouble( s.nextToken( ) ));
         i++;
      }
      JFreeChart chart = ChartFactory.createPieChart( 
         "Mobile Sales",  // chart title           
         dataset,         // data           
         true,            // include legend           
         true,           
         false);
      
      int width = 560; /* Width of the image */          
      int height = 370; /* Height of the image */                          
      File pieChart = new File( "pie_Chart.jpeg" );                        
      ChartUtilities.saveChartAsJPEG( pieChart, chart, width, height); 
   }
}

Let us keep the above Java code in PieChart_File.java file, and then compile and run it from command prompt as follows :

$javac PieChart_File.java 
$java PieChart_File 

If everything is fine , it will compile and run to create JPEG image file named PieChart.jpeg that contains following chart.

JFreeChart File Interface

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