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将 DefaultCategoryDataset 转换为 CategoryDataset

Java问题
2022-01-01

cast DefaultCategoryDataset to CategoryDataset(将 DefaultCategoryDataset 转换为 CategoryDataset)

本文介绍了将 DefaultCategoryDataset 转换为 CategoryDataset的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我正在尝试创建一个基本的条形图，当我编译它时会出现类似的错误

<块引用>

线程主"java.lang.ClassCastException 中的异常:org.jfree.data.category.DefaultCategoryDataset 不能转换为org.jfree.data.CategoryDataset

这是我的代码

 包条形图；导入 java.awt.Color；导入 java.awt.Dimension；导入 org.jfree.chart.ChartFactory；导入 org.jfree.chart.ChartPanel；导入 org.jfree.chart.JFreeChart；导入 org.jfree.chart.plot.PlotOrientation；导入 org.jfree.data.category.CategoryDataset；导入 org.jfree.data.category.DefaultCategoryDataset；导入 org.jfree.ui.ApplicationFrame；公共类 BarChartDemo 扩展公共 BarChartDemo(最终字符串标题){超级(标题)；最终 CategoryDataset 数据集 = createDataset();最终 JFreeChart 图表 = createChart(dataset);最终的 ChartPanel chartPanel = new ChartPanel(chart);chartPanel.setPreferredSize(新维度(500, 270));设置内容窗格(图表面板)；}公共静态无效主要(字符串[]参数){BarChartDemo br = new BarChartDemo("title");br.createDataset();}私有类别数据集 createDataset() {//行键...最终字符串 series1 = 第一"；最终字符串 series2 = "第二个";最终字符串 series3 = "第三";//列键...最终字符串 category1 = "类别 1";最终字符串 category2 = "类别 2";最终字符串 category3 = "类别 3";最终字符串 category4 = "类别 4";最终字符串 category5 = "Category 5";//创建数据集...最终 DefaultCategoryDataset 数据集 = 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);返回数据集；}私人 JFreeChart createChart(最终 CategoryDataset 数据集){//创建图表...最终 JFreeChart 图表 = ChartFactory.createBarChart("Bar Chart Demo",//图表标题"Category",//域轴标签值"，(org.jfree.data.CategoryDataset)数据集，PlotOrientation.VERTICAL,//方向true,//包括图例true,//工具提示?假//网址?);chart.setBackgroundPaint(Color.white);返回图表；}}

为什么我们不能将 DefaultCategoryDataset 转换为 CategoryDataset，我可以纠正谁?

解决方案

经过测试的代码:

导入java.awt.Color；导入 java.awt.Dimension；导入 java.awt.EventQueue；导入 org.jfree.chart.ChartFactory；导入 org.jfree.chart.ChartPanel；导入 org.jfree.chart.JFreeChart；导入 org.jfree.chart.plot.PlotOrientation；导入 org.jfree.data.category.CategoryDataset；导入 org.jfree.data.category.DefaultCategoryDataset；导入 org.jfree.ui.ApplicationFrame；公共类 BarChartDemo 扩展 ApplicationFrame {公共 BarChartDemo(最终字符串标题){超级(标题)；最终 CategoryDataset 数据集 = createDataset();最终 JFreeChart 图表 = createChart(dataset);最终 ChartPanel chartPanel = new ChartPanel(chart) {@覆盖公共维度 getPreferredSize() {返回新维度(500, 270)；}};设置内容窗格(图表面板)；盒();设置可见(真)；}公共静态无效主要(字符串[]参数){EventQueue.invokeLater(new Runnable() {@覆盖公共无效运行(){BarChartDemo br = new BarChartDemo("title");}});}私有类别数据集 createDataset() {//行键...最终字符串 series1 = 第一"；最终字符串 series2 = "第二个";最终字符串 series3 = "第三";//列键...最终字符串 category1 = "类别 1";最终字符串 category2 = "类别 2";最终字符串 category3 = "类别 3";最终字符串 category4 = "类别 4";最终字符串 category5 = "Category 5";//创建数据集...最终 DefaultCategoryDataset 数据集 = 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);返回数据集；}私人 JFreeChart createChart(最终 CategoryDataset 数据集){//创建图表...最终 JFreeChart 图表 = ChartFactory.createBarChart("Bar Chart Demo",//图表标题"Category",//域轴标签价值"，数据集，PlotOrientation.VERTICAL,//方向true,//包括图例true,//工具提示?假//网址?);chart.setBackgroundPaint(Color.white);返回图表；}}

I'm trying to create a basic barchart and when I compile it gives an error like

Exception in thread "main" java.lang.ClassCastException: org.jfree.data.category.DefaultCategoryDataset cannot be cast to org.jfree.data.CategoryDataset

here is my 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;

    }
}

why cann't we cast DefaultCategoryDataset to CategoryDataset and who can I correct this ?

解决方案

The fully qualified name of CategoryDataset is org.jfree.data.category.CategoryDataset, but the cast is superfluous in this context.

Code, as tested:

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;
    }
}

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