How to Draw Multiple Lines in Java Swing?

Question

How can I draw multiple lines using Java Swing?

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

public class MultiLineDrawing extends JPanel {
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.BLUE);

        for (int i = 0; i < 10; i++) {
            g2d.drawLine(10, 10 + i * 10, 200, 10 + i * 10);
        }
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Draw Multiple Lines");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 300);
        frame.add(new MultiLineDrawing());
        frame.setVisible(true);
    }
}

Answer

Drawing multiple lines in Java Swing can be achieved using the `Graphics` or `Graphics2D` class within a custom `JPanel`. By overriding the `paintComponent` method, you can execute custom drawing logic to create multiple lines dynamically based on your requirements.

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

public class MultiLineDrawing extends JPanel {
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.BLUE);

        for (int i = 0; i < 10; i++) {
            g2d.drawLine(10, 10 + i * 10, 200, 10 + i * 10);
        }
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Draw Multiple Lines");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 300);
        frame.add(new MultiLineDrawing());
        frame.setVisible(true);
    }
}

Causes

Not overriding the `paintComponent` method in a JPanel.
Improper use of the Graphics context which can lead to unexpected results.

Solutions

Use a `JPanel` and override the `paintComponent` method for custom drawings.
Use a loop to manage the drawing of multiple lines spatially on the panel.

Common Mistakes

Mistake: Forgetting to call super.paintComponent(g) in the overridden method.

Solution: Always call the superclass method to ensure proper rendering.

Mistake: Using fixed coordinates without proper scaling

Solution: Use relative positioning or calculate positions dynamically.

Helpers

Java Swing
Draw lines Java
Java graphics drawing
Swing JPanel
Graphics Java tutorial