I had tried to add an if-else statement to change the color of the text. However, it does not work well. I hope to change only marks below 40 to become red, but I don't know why all my text changed to red. May I know what is the mistake I make?

In the if-else statement, I write the code to change the color of the text when mark is below 40. However, it changes all the text to red.

import java.awt.*;
import javax.swing.*;
import javax.swing.table.*;


public class testing{

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                mark();
            }
        });
    }

    public static void mark() {

        String[] columns = new String[] {"Name", "Marks(%)"};

        Object[][] data= new Object[][] {
                {"Aby", "100"},
                {"Amy", "30"}
        };

        JFrame frame = new JFrame("Student Marks List");
        frame.setVisible(true);
        frame.setSize(600, 500);
        frame.setLayout(new BorderLayout());

        Panel details = new Panel(null);
        details.setBounds(0,50, 1000, 125);

        Panel contents = new Panel(null);
        contents.setBounds(0,50, 1000, 600);

        frame.add(details, BorderLayout.NORTH);
        frame.add(contents, BorderLayout.CENTER);

        JTable tb1;
        tb1 = new JTable(data, columns);
        JScrollPane sp = new JScrollPane(tb1);

        tb1.getTableHeader().setOpaque(false);
        tb1.getTableHeader().setFont(new Font("Barlow Condensed ExtraBold", Font.BOLD, 20));
        tb1.getTableHeader().setPreferredSize(new Dimension(100, 30));
        tb1.setFont(new Font("Barlow Condensed", Font.BOLD, 20));
        tb1.setRowHeight(30);

        for (int i = 0; i < tb1.getRowCount(); i  ) {
            Object x = tb1.getValueAt(i, 1);
            String y = x.toString();
            double z = Double.parseDouble(y);
            if (z < 40) {
                tb1.setForeground(Color.RED);
            }
            else {
                tb1.setForeground(new Color(38, 120, 81));
            }
        }

        DefaultTableCellRenderer centerRenderer = new DefaultTableCellRenderer();
        centerRenderer.setHorizontalAlignment(JLabel.CENTER);

        tb1.setBounds(25,10,200,375);
        sp.setBounds(25,10,200,375);
        contents.add(sp);

    }

}

CodePudding user response：

Create a cell renderer that takes a condition and colors for true and false. Assign this cell renderer to the column.

    TableColumn col = tb1.getColumnModel().getColumn(1);
    col.setCellRenderer(new CellRenderer(v -> v < 40d, Color.RED, new Color(38, 120, 81)));

The cell renderer

class CellRenderer extends DefaultTableCellRenderer {
    DoublePredicate condition;
    Color fgFalse;
    Color fgTrue;

    public CellRenderer(DoublePredicate condition, Color fgFalse, Color fgTrue) {
        super();
        this.condition = condition;
        this.fgFalse = fgFalse;
        this.fgTrue = fgTrue;
    }

    @Override
    public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
        Component cell = super.getTableCellRendererComponent(table, value, isSelected, hasFocus, row, column);
        cell.setForeground(condition.test((Double)value) ? fgTrue : fgFalse);
        return cell;
    }
}