Question

I have searched everywhere and I just cant find the answer.
How do I rotate a Rectangle in java?

Here is some of my code:

package net.chrypthic.Space;

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

public class Space extends JPanel implements ActionListener{
    Timer time;
    public Space()
    {
        setVisible(true);
        setFocusable(true);
        addMouseMotionListener(new ML());
        addMouseListener(new ML());
        addKeyListener(new AL());
        time=new Timer(5, this);
        time.start();
    }
    public void paint(Graphics g)
    {
        super.paint(g);
        Graphics2D g2d = (Graphics2D)g;
        g2d.setColor(Color.WHITE);
        Rectangle rect2 = new Rectangle(100, 100, 20, 20);

        g2d.draw(rect2);
        g2d.fill(rect2);
    }
    public void actionPerformed(ActionEvent ae) {
        repaint();
    }
    public class AL extends KeyAdapter
    {
        public void keyPressed(KeyEvent e) {
        }

        public void keyReleased(KeyEvent e) {
        }
    }
    public class ML extends MouseAdapter
    {
        public void mouseMoved(MouseEvent e) {
        }

        public void mousePressed(MouseEvent e){
        }
    }
}

I tried g2d.rotate(100D); but it didnt work.
Thanks in advance.

Here’s my edited code:

package net.chrypthic.Space;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Space extends JPanel implements ActionListener{
    Timer time;
    public Space()
    {
        setVisible(true);
        setFocusable(true);
        setSize(640, 480);
        setBackground(Color.BLACK);
        time=new Timer(5, this);
        time.start();
    }
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D)g;
        Rectangle rect1 = new Rectangle(100, 100, 20, 20);
        g2d.setColor(Color.WHITE);
        g2d.translate(rect1.x+(rect1.width/2), rect1.y+(rect1.height/2));
        g2d.rotate(Math.toRadians(90));
        g2d.draw(rect1);
        g2d.fill(rect1);
    }
    public void actionPerformed(ActionEvent e) 
    {
        repaint();
    }
}

Answer 1

For images you have to use drawImage method of Graphics2D with the relative AffineTransform.

For shape you can rotate Graphics2D itself:

public void paintComponent(Graphics g)
{
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D)g;
    g2d.setColor(Color.WHITE);
    Rectangle rect2 = new Rectangle(100, 100, 20, 20);

    g2d.rotate(Math.toRadians(45));
    g2d.draw(rect2);
    g2d.fill(rect2);
}

And btw, you should override paintComponent method instead of paint.

Citing JComponent‘s API:

Invoked by Swing to draw components. Applications should not invoke
paint directly, but should instead use the repaint method to schedule
the component for redrawing.

This method actually delegates the work of painting to three
protected methods: paintComponent, paintBorder, and paintChildren.
They’re called in the order listed to ensure that children appear on
top of component itself. Generally speaking, the component and its
children should not paint in the insets area allocated to the border.
Subclasses can just override this method, as always. A subclass that
just wants to specialize the UI (look and feel) delegate’s paint
method should just override paintComponent.

Remember also than when you perform an affine transformation, like a rotation, the object is implicitly rotated around the axis origin. So if your intent is to rotate it around an arbitrary point, you should before translating it back to the origin, rotate it, and then re-traslating it to the desired point.