Guss DefaultCategoryDataset zu CategoryDataset

Question

Ich versuche, eine grundlegende barchart zu erstellen und wenn ich kompilieren es gibt einen Fehler wie

Exception in thread "main" java.lang.ClassCastException: org.jfree.data. category.DefaultCategoryDataset nicht

hier org.jfree.data.CategoryDataset gegossen werden ist mein Code

package barchart; 

import java.awt.Color; 
import java.awt.Dimension; 

import org.jfree.chart.ChartFactory; 
import org.jfree.chart.ChartPanel; 
import org.jfree.chart.JFreeChart; 
import org.jfree.chart.plot.PlotOrientation; 
import org.jfree.data.category.CategoryDataset; 
import org.jfree.data.category.DefaultCategoryDataset; 
import org.jfree.ui.ApplicationFrame; 


public class BarChartDemo extends 
    public BarChartDemo(final String title) { 

     super(title); 

     final CategoryDataset dataset = createDataset(); 
     final JFreeChart chart = createChart(dataset); 
     final ChartPanel chartPanel = new ChartPanel(chart); 
     chartPanel.setPreferredSize(new Dimension(500, 270)); 
     setContentPane(chartPanel); 

    } 
    public static void main(String[] args) { 
     BarChartDemo br = new BarChartDemo("title"); 
     br.createDataset(); 
    } 


    private CategoryDataset createDataset() { 

     // row keys... 
     final String series1 = "First"; 
     final String series2 = "Second"; 
     final String series3 = "Third"; 

     // column keys... 
     final String category1 = "Category 1"; 
     final String category2 = "Category 2"; 
     final String category3 = "Category 3"; 
     final String category4 = "Category 4"; 
     final String category5 = "Category 5"; 

     // create the dataset... 
     final DefaultCategoryDataset dataset = new DefaultCategoryDataset(); 

     dataset.addValue(1.0, series1, category1); 
     dataset.addValue(4.0, series1, category2); 
     dataset.addValue(3.0, series1, category3); 
     dataset.addValue(5.0, series1, category4); 
     dataset.addValue(5.0, series1, category5); 

     dataset.addValue(5.0, series2, category1); 
     dataset.addValue(7.0, series2, category2); 
     dataset.addValue(6.0, series2, category3); 
     dataset.addValue(8.0, series2, category4); 
     dataset.addValue(4.0, series2, category5); 

     dataset.addValue(4.0, series3, category1); 
     dataset.addValue(3.0, series3, category2); 
     dataset.addValue(2.0, series3, category3); 
     dataset.addValue(3.0, series3, category4); 
     dataset.addValue(6.0, series3, category5); 

     return dataset; 

    } 


    private JFreeChart createChart(final CategoryDataset dataset) { 

     // create the chart... 
     final JFreeChart chart = ChartFactory.createBarChart(
      "Bar Chart Demo",   // chart title 
      "Category",    // domain axis label 
      "Value", (org.jfree.data.CategoryDataset) dataset,     
      PlotOrientation.VERTICAL, // orientation 
      true,      // include legend 
      true,      // tooltips? 
      false      // URLs? 
     ); 

     chart.setBackgroundPaint(Color.white); 
     return chart; 

    } 
} 

Warum können wir DefaultCategoryDataset nicht in CategoryDataset umwandeln und wer kann das korrigieren?

Answer 1

Der vollständig qualifizierte Name CategoryDataset ist org.jfree.data.category.CategoryDataset, aber die Besetzung ist in diesem Zusammenhang überflüssig.

-Code, wie geprüft:

import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.EventQueue; 
import org.jfree.chart.ChartFactory; 
import org.jfree.chart.ChartPanel; 
import org.jfree.chart.JFreeChart; 
import org.jfree.chart.plot.PlotOrientation; 
import org.jfree.data.category.CategoryDataset; 
import org.jfree.data.category.DefaultCategoryDataset; 
import org.jfree.ui.ApplicationFrame; 

public class BarChartDemo extends ApplicationFrame { 

    public BarChartDemo(final String title) { 
     super(title); 
     final CategoryDataset dataset = createDataset(); 
     final JFreeChart chart = createChart(dataset); 
     final ChartPanel chartPanel = new ChartPanel(chart) { 

      @Override 
      public Dimension getPreferredSize() { 
       return new Dimension(500, 270); 
      } 
     }; 
     setContentPane(chartPanel); 
     pack(); 
     setVisible(true); 
    } 

    public static void main(String[] args) { 
     EventQueue.invokeLater(new Runnable() { 

      @Override 
      public void run() { 
       BarChartDemo br = new BarChartDemo("title"); 
      } 
     }); 
    } 

    private CategoryDataset createDataset() { 
     // row keys... 
     final String series1 = "First"; 
     final String series2 = "Second"; 
     final String series3 = "Third"; 

     // column keys... 
     final String category1 = "Category 1"; 
     final String category2 = "Category 2"; 
     final String category3 = "Category 3"; 
     final String category4 = "Category 4"; 
     final String category5 = "Category 5"; 

     // create the dataset... 
     final DefaultCategoryDataset dataset = new DefaultCategoryDataset(); 

     dataset.addValue(1.0, series1, category1); 
     dataset.addValue(4.0, series1, category2); 
     dataset.addValue(3.0, series1, category3); 
     dataset.addValue(5.0, series1, category4); 
     dataset.addValue(5.0, series1, category5); 

     dataset.addValue(5.0, series2, category1); 
     dataset.addValue(7.0, series2, category2); 
     dataset.addValue(6.0, series2, category3); 
     dataset.addValue(8.0, series2, category4); 
     dataset.addValue(4.0, series2, category5); 

     dataset.addValue(4.0, series3, category1); 
     dataset.addValue(3.0, series3, category2); 
     dataset.addValue(2.0, series3, category3); 
     dataset.addValue(3.0, series3, category4); 
     dataset.addValue(6.0, series3, category5); 

     return dataset; 
    } 

    private JFreeChart createChart(final CategoryDataset dataset) { 
     // create the chart... 
     final JFreeChart chart = ChartFactory.createBarChart(
      "Bar Chart Demo", // chart title 
      "Category", // domain axis label 
      "Value", dataset, 
      PlotOrientation.VERTICAL, // orientation 
      true, // include legend 
      true, // tooltips? 
      false // URLs? 
     ); 
     chart.setBackgroundPaint(Color.white); 
     return chart; 
    } 
}