Thread: Double check on Java code.

Alright - I downloaded a *.class file that was being used as an applet and decompiled it into this. I need to make a flow chart of what every line in this program does and why, so that I can figure out how to solve the same problem this program does, but in C++, and in my own style. This is a pretty easy question, but I just want to double check. Can anyone find a place in this code where fill() might be called? Even if it's in an IF statement, I just need to find it, because my with my understanding of this code so far, fill() is just a useless function!

Code:

import java.applet.Applet;
import java.awt.*;

public class lsq extends Applet
{

    public void init()
    {
        setBackground(Color.lightGray);
        setLayout(null);
        resize(475, 375);
        label = new Label(" Data");
        label.reshape(0, 0, 150, 20);
        add(label);
        label = new Label(" Plot");
        label.reshape(155, 0, 270, 20);
        add(label);
        data.reshape(0, 20, 150, 150);
        data.setFont(new Font("COURIER", 0, 12));
        add(data);
        plot1.reshape(155, 20, 320, 230);
        add(plot1);
        plot1.repaint();
        label = new Label(" Equation");
        label.reshape(0, 250, 470, 20);
        add(label);
        result.reshape(0, 270, 475, 75);
        result.setFont(new Font("COURIER", 0, 12));
        add(result);
        cpanel.reshape(0, 350, 475, 75);
        cpanel.add(compute);
        cpanel.add(plotData);
        model.addItem("Linear");
        model.addItem("Quadratic");
        model.addItem("Cubic");
        cpanel.add(model);
        add(cpanel);
        show();
    }

    public boolean action(Event event, Object obj)
    {
        if(event.target == compute)
        {
            result.setText("Calculating...");
            Matrix matrix = new Matrix(data.getText());
            plot1.P = matrix;
            plot1.repaint();
            result.setText(compute(matrix));
        } else
        if(event.target == plotData)
        {
            plot1.M = new Matrix("0;0");
            plot1.P = new Matrix(data.getText());
            plot1.repaint();
        }
        return super.action(event, obj);
    }

    String compute(Matrix matrix)
    {
        int k = model.getSelectedIndex() + 2;
        Matrix matrix1 = new Matrix(matrix.rows, k, 1.0D);
        for(int j1 = 1; j1 < matrix1.columns; j1++)
        {
            for(int i = 0; i < matrix1.rows; i++)
                matrix1.element[i][j1] = Math.pow(matrix.element[i][0], j1);

        }

        Matrix matrix2 = matrix1.Q();
        Matrix matrix3 = new Matrix(matrix2.transpose(), matrix1, '*');
        Matrix matrix4 = new Matrix(matrix2.transpose(), matrix.sub(0, matrix.rows - 1, 1, 1), '*');
        matrix4 = new Matrix(matrix4.sub(0, matrix3.columns - 1, 0, 0));
        matrix3 = new Matrix(matrix3.sub(0, matrix3.columns - 1, 0, matrix3.columns - 1));
        Matrix matrix5 = new Matrix(matrix3, matrix4, '\\');
        plot1.P = new Matrix(data.getText());
        plot1.repaint();
        plot1.M = matrix5;
        matrix4 = matrix.sub(0, matrix.rows - 1, 1, 1);
        double d = matrix4.average();
        double d1 = 0.0D;
        double d3 = 0.0D;
        double d4 = 0.0D;
        for(int j = 0; j < matrix.rows; j++)
        {
            double d2 = 0.0D;
            for(int l = 0; l < matrix5.rows; l++)
                d2 += matrix5.element[l][0] * Math.pow(matrix.element[j][0], l);

            d3 += Math.pow(d2 - d, 2D);
            d4 += Math.pow(matrix4.element[j][0] - d, 2D);
        }

        Matrix matrix6 = new Matrix(matrix1, matrix5, '*');
        Matrix matrix7 = new Matrix(matrix6, matrix4, '-');
        double d5 = Math.pow(matrix7.norm(), 2D);
        String s = "\ny = " + matrix5.element[0][0];
        if(matrix5.element[1][0] >= 0.0D)
            s = s + " +";
        s = s + " " + matrix5.element[1][0] + "x";
        for(int i1 = 2; i1 < matrix5.rows; i1++)
        {
            if(matrix5.element[i1][0] >= 0.0D)
                s = s + " +";
            s = s + " " + matrix5.element[i1][0] + "x^" + i1;
        }

        return s;
    }

    String fill(double d, int i)
    {
        String s = " " + d + "                                             ";
        return s.substring(0, i);
    }

    public lsq()
    {
        data = new TextArea(30, 20);
        result = new TextArea(50, 20);
        plot1 = new Plot();
        cpanel = new Panel();
        compute = new Button("Compute");
        plotData = new Button("Plot data");
        model = new Choice();
    }

    TextArea data;
    TextArea result;
    Plot plot1;
    Panel cpanel;
    Button compute;
    Button plotData;
    Choice model;
    Label label;
}