Java 将DefaultCategoryDataset强制转换为CategoryDataset
我试图创建一个基本的柱状图,当我编译它时,会出现如下错误 线程“main”java.lang.ClassCastException中的异常: org.jfree.data.category.DefaultCategoryDataset不能强制转换为 org.jfree.data.CategoryDataset 这是我的密码Java 将DefaultCategoryDataset强制转换为CategoryDataset,java,casting,dataset,jfreechart,Java,Casting,Dataset,Jfreechart,我试图创建一个基本的柱状图,当我编译它时,会出现如下错误 线程“main”java.lang.ClassCastException中的异常: org.jfree.data.category.DefaultCategoryDataset不能强制转换为 org.jfree.data.CategoryDataset 这是我的密码 package barchart; import java.awt.Color; import java.awt.Dimension; import org.jfree
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;
}
}
为什么我们不能将DefaultCategoryDataset转换为CategoryDataset,我可以纠正谁的错误?的完全限定名是org.jfree.data.category.CategoryDataset,但在这种情况下转换是多余的 测试代码:
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;
}
}
的完全限定名是
org.jfree.data.category.CategoryDataset
,但在这种情况下强制转换是多余的
测试代码:
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;
}
}