JFreeChart 或 Chart.js 库代码示例：从 Excel 文件读取数据并创建图表

使用 JFreeChart 库创建图表

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.DateAxis;
import org.jfree.chart.axis.NumberAxis;
import org.jfree.chart.plot.CombinedDomainXYPlot;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.plot.XYPlot;
import org.jfree.data.time.Day;
import org.jfree.data.time.TimeSeries;
import org.jfree.data.time.TimeSeriesCollection;
import org.jfree.data.xy.XYDataset;
import org.jfree.ui.ApplicationFrame;
import org.jfree.ui.RefineryUtilities;

import java.awt.*;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class JFreeChartsExample extends ApplicationFrame {

    public JFreeChartsExample(String title) throws IOException, ParseException {
        super(title);
        JFreeChart chart = createChart();
        ChartPanel panel = new ChartPanel(chart);
        panel.setPreferredSize(new java.awt.Dimension(800, 600));
        setContentPane(panel);
    }

    private JFreeChart createChart() throws IOException, ParseException {
        XYDataset dataset1 = createDataset('input.xlsx', 'P1');

        DateAxis timeAxis = new DateAxis('Time');
        timeAxis.setDateFormatOverride(new SimpleDateFormat('yyyy-MM-dd'));

        NumberAxis valueAxis1 = new NumberAxis('Value');
        NumberAxis valueAxis2 = new NumberAxis('Secondary Value');

        XYPlot plot = new XYPlot(dataset1, timeAxis, valueAxis1, null);
        plot.setOrientation(PlotOrientation.VERTICAL);

        XYDataset dataset2 = createDataset('input.xlsx', 'P1');
        plot.setDataset(1, dataset2);
        plot.setRangeAxis(1, valueAxis2);
        plot.mapDatasetToRangeAxis(1, 1);

        JFreeChart chart = new JFreeChart('Chart', JFreeChart.DEFAULT_TITLE_FONT, plot, true);
        chart.setBackgroundPaint(Color.white);

        return chart;
    }

    private XYDataset createDataset(String filename, String sheetName) throws IOException, ParseException {
        TimeSeries series1 = new TimeSeries('Value');
        TimeSeries series2 = new TimeSeries('Secondary Value');

        InputStream inputStream = new FileInputStream(filename);
        Workbook workbook = WorkbookFactory.create(inputStream);
        Sheet sheet = workbook.getSheet(sheetName);

        for (int i = 1; i <= 50; i++) {
            Row row = sheet.getRow(i);
            Cell dateCell = row.getCell(0);
            Cell valueCell1 = row.getCell(1);
            Cell valueCell2 = row.getCell(2);

            Date date = dateCell.getDateCellValue();
            double value1 = valueCell1.getNumericCellValue();
            double value2 = valueCell2.getNumericCellValue();

            Day day = new Day(date);
            series1.add(day, value1);
            series2.add(day, value2);
        }

        TimeSeriesCollection dataset = new TimeSeriesCollection();
        dataset.addSeries(series1);
        dataset.addSeries(series2);

        return dataset;
    }

    public static void main(String[] args) {
        try {
            JFreeChartsExample example = new JFreeChartsExample('Chart Example');
            example.pack();
            RefineryUtilities.centerFrameOnScreen(example);
            example.setVisible(true);
        } catch (IOException | ParseException e) {
            e.printStackTrace();
        }
    }
}

使用 Chart.js 库创建图表

<!DOCTYPE html>
<html>
<head>
    <title>Chart.js Example</title>
    <script src='https://cdn.jsdelivr.net/npm/chart.js'></script>
</head>
<body>
    <canvas id='chart'></canvas>

    <script>
        const ctx = document.getElementById('chart').getContext('2d');

        fetch('input.xlsx')
            .then(response => response.arrayBuffer())
            .then(data => {
                const workbook = XLSX.read(data, {type: 'array'});
                const sheet = workbook.Sheets['P1'];
                const dates = XLSX.utils.sheet_to_json(sheet, {header: 1, range: 'A2:A50'});
                const values1 = XLSX.utils.sheet_to_json(sheet, {header: 1, range: 'B2:B50'});
                const values2 = XLSX.utils.sheet_to_json(sheet, {header: 1, range: 'C2:C50'});

                const labels = dates.map(date => new Date(date));
                const data1 = values1.map(value => parseFloat(value));
                const data2 = values2.map(value => parseFloat(value));

                new Chart(ctx, {
                    type: 'line',
                    data: {
                        labels: labels,
                        datasets: [
                            {
                                label: 'Value',
                                data: data1,
                                borderColor: 'blue',
                                fill: false
                            },
                            {
                                label: 'Secondary Value',
                                data: data2,
                                borderColor: 'red',
                                fill: false
                            }
                        ]
                    },
                    options: {
                        scales: {
                            x: {
                                type: 'time',
                                time: {
                                    unit: 'day',
                                    displayFormats: {
                                        day: 'yyyy-MM-dd'
                                    }
                                },
                                ticks: {
                                    source: 'labels'
                                }
                            },
                            y: {
                                beginAtZero: true
                            }
                        }
                    }
                });
            });
    </script>
</body>
</html>

注意:

对于 Chart.js 的代码，你需要引入 Chart.js 库，并使用 fetch 函数来加载 Excel 文件。
Chart.js 需要在浏览器中运行，所以你需要将代码保存为一个 HTML 文件并在浏览器中打开。
为了使用 XLSX 库解析 Excel 文件，你需要在 HTML 文件中添加以下代码：

<script src='https://cdn.jsdelivr.net/npm/xlsx'></script>

JFreeChart 或 Chart.js 库代码示例：从 Excel 文件读取数据并创建图表