Add Trendline to Chart and Read Trendline Equation in Excel in Java

import com.spire.xls.*;
import com.spire.xls.core.IChartTrendLine;

import java.awt.*;

public class AddTrendline {
    public static void main(String[] args){
        //Create a Workbook instance
        Workbook workbook = new Workbook();
        //Load the Excel file
        workbook.loadFromFile("test.xlsx");

        //Get the first chart in the first worksheet
        Chart chart = workbook.getWorksheets().get(0).getCharts().get(0);

        //Add a Trendline to the first series of the chart
        IChartTrendLine trendLine = chart.getSeries().get(0).getTrendLines().add(TrendLineType.Linear);

        //Set Trendline name
        trendLine.setName("Linear(Series1)");
        //Set line type and color
        trendLine.getBorder().setPattern(ChartLinePatternType.DashDot);
        trendLine.getBorder().setColor(Color.blue);
        //Set forward and backward value
        trendLine.setForward(0.5);
        trendLine.setBackward(0.5);
        //Set intercept value
        trendLine.setIntercept(5);

        //Display equation on chart
        trendLine.setDisplayEquation(true);
        //Display R-Squared value on chart
        trendLine.setDisplayRSquared(true);

        //Save the result file
        workbook.saveToFile("AddTrendline.xlsx", ExcelVersion.Version2013);
    }
}

import com.spire.xls.Chart;
import com.spire.xls.Workbook;
import com.spire.xls.core.IChartTrendLine;

public class ReadEquationOfTrendline {
    public static void main(String[] args){
        //Create a Workbook instance
        Workbook workbook = new Workbook();
        //Load the Excel file
        workbook.loadFromFile("AddTrendline.xlsx");

        //Get the first chart in the first worksheet
        Chart chart = workbook.getWorksheets().get(0).getCharts().get(0);

        //Read the equation of the first series of the chart
        IChartTrendLine trendLine = chart.getSeries().get(0).getTrendLines().get(0);
        String equation = trendLine.getFormula();
        System.out.println("The equation is: " + equation);
    }
}