import java.io.File;   
import java.io.FileInputStream;   
import java.io.InputStreamReader;   
import java.io.BufferedReader;   
import java.io.*;   
import java.util.*;   
import java.lang.NumberFormatException;   
import java.text.NumberFormat;   
import java.text.MessageFormat;   

import java.awt.Font;   
import javax.swing.JFrame;   
import javax.swing.JPanel;   
import org.jfree.chart.ChartFactory;   
import org.jfree.chart.ChartPanel;   
import org.jfree.chart.JFreeChart;   
import org.jfree.chart.plot.PiePlot;   
import org.jfree.data.general.DefaultPieDataset;   

import org.jfree.chart.ChartFactory;   
import org.jfree.chart.ChartPanel;   
import org.jfree.chart.JFreeChart;   
import org.jfree.chart.axis.NumberAxis;   
import org.jfree.chart.plot.PlotOrientation;   
import org.jfree.chart.plot.XYPlot;   
import org.jfree.chart.renderer.xy.StandardXYItemRenderer;   
import org.jfree.data.*;   
import org.jfree.data.xy.XYDataset;   
import org.jfree.data.xy.XYSeries;   
import org.jfree.data.xy.XYSeriesCollection;   
import org.jfree.data.DomainOrder;   
import org.jfree.data.general.SeriesDataset;   
import org.jfree.data.category.DefaultCategoryDataset;   


public class graph extends JFrame{   

	/**
	 * 
	 */
	private static final long serialVersionUID = 0L;

	public graph(String title) throws Exception{   

		super(title);   

		XYDataset dataset = createDataset();   
		JFreeChart chart = createChart(dataset);   
		ChartPanel chartPanel = new ChartPanel(chart);   
		chartPanel.setPreferredSize(new java.awt.Dimension(500, 270));   
		setContentPane(chartPanel);   
		chartPanel.setMouseZoomable(true, false);   
	}   


	// Well, here I read a file from a table in txt each line with 4 columns of numbers), save it in a string and then on a string 
	// Array of 4 elements. Then convert each element of the string to double (not know if I'm being very stupid, I am more beginner in java ...) 
	// What I'm trying to do is get two of those column (now in double) and put points on the method series.add below 
	// I think I have to do a loop of some way, then do what you suggested q ... But the loop that I did overwrite the variables 
	// My attempt was a normal access to the txt file

	/* public extrator extract(String) throws Exception {  
        File file = new File("F:\\Ekralog.txt");      
        FileInputStream in = new FileInputStream(file);  
        InputStreamReader convert = new InputStreamReader(in);  
        BufferedReader bf = new BufferedReader(convert);  
        String line;  
        String[] element;  
        line = bf.readLine();  
        element = line.split("[\\s]+");  
        bf.close();  
        in.close();return  

	 */   


	private XYDataset createDataset() throws Exception {   
		//CONVERT STRING TO DOUBLE   
		//double element0;     
		//element0 = Double.parseDouble(element[0]); /* element[0] its one string*/   

		XYSeries series1 = new XYSeries("TRZ");   
		series1.add(1.0, 1.0); // some point that i've inserted to test and it is
		series1.add(2.0, 4.0);// should i do a loop to test it.. there are more than 100 points
		series1.add(3.0, 3.0);   
		series1.add(4.0, 5.0);   
		series1.add(5.0, 5.0);   
		series1.add(6.0, 7.0);   
		series1.add(7.0, 7.0);   
		series1.add(8.0, 8.0);   



		XYSeriesCollection dataset = new XYSeriesCollection();   
		dataset.addSeries(series1);   

		return dataset;   


	}   
	// ListDouble colunas = new ArrayListDouble();   

	//public ListDouble getColunas(){   

	//    return colunas;   

	// }   


	private JFreeChart createChart(XYDataset dataset) {   
		// create the chart...   
		JFreeChart chart = ChartFactory.createXYLineChart(   
				"Medida", // chart title   
				"X", // x axis label   
				"Y", // y axis label   
				dataset, // data   
				PlotOrientation.VERTICAL,   
				true, // include legend   
				true, // tooltips   
				false // urls   

		);   

		return chart;   
	}   

	public static void main(String[] args) throws Exception {   
		graph teste = new graph("test");   
		teste.pack();   
		teste.setVisible(true);   
	}   

}

private CategoryDataset createDataset() throws Exception {
 
    DefaultCategoryDataset dataset = new DefaultCategoryDataset();
    dataset.addValue(255, "Errors", "error1");
    dataset.addValue(34, "Errors", "error2");
    dataset.addValue(111, "Errors", "error5");
    dataset.addValue(23, "Errors", "error3");
 
    return dataset;
}
 
private JFreeChart createChart(CategoryDataset dataset) {
    // create the chart...
    JFreeChart chart = ChartFactory.createLineChart(
            "Medida", // chart title
            "Error Code", // x axis label
            "Count", // y axis label
            dataset, // data
            PlotOrientation.VERTICAL,
            true, // include legend
            true, // tooltips
            false // urls
    );
 
    return chart;
}

JFreeChart chart = ChartFactory.createBarChart(