How would I make my image rotate using key listener?

Question

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

public class SpaceInvaders extends JPanel implements ActionListener, KeyListener {
    //Declare global variables
    private Asteroids asteroid;
    private int xDir, yDir;
    private Timer t;
    private Spaceship ship;

    public static void main(String[] args) {
        new SpaceInvaders();
    }

    public SpaceInvaders() {
        ship = new Spaceship(600,500, new ImageIcon("ship2.png"));

        //Declare and initialize Ball object
        asteroid = new Asteroids(100,100, new ImageIcon("Asteroids.png"));

        //Initialize the two variables that will determine how many pixels the ball
        //will move horizontally and vertically
        xDir = 1;
        yDir = 3;

        //Initialize Timer object and set interval to 50 milliseconds
        t = new Timer(20, this);

        //Set properties of JPanel object
        setLayout(null);
        setBackground(Color.BLACK);
        addKeyListener(this);
        setFocusable(true);

        //Declare, initialize and set properties of JFrame
        JFrame frame = new JFrame();
        frame.setContentPane(this);
        frame.setSize(1200,1000);
        frame.setTitle("Space Invaders");
        frame.setResizable(false);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);


        //Start the timer
        t.start();   
    }

    public void actionPerformed(ActionEvent e) {
        repaint();
    }

    public void paintComponent(Graphics g)
    {
    // Draw the image on the screen
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g;
    g2.drawImage(asteroid.getImage(), asteroid.getX(), asteroid.getY(),this);
    ship.draw(g2);
    }

    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode() == KeyEvent.VK_RIGHT)
        {
        }
        else if (e.getKeyCode() == KeyEvent.VK_LEFT)
        {
        }
    }
    public void keyTyped(KeyEvent e) {}
    public void keyReleased(KeyEvent e) {}
}

Ive tried alot of things and i found no clear answer on the internet, was wondering if i could get some help please. I know that i have to use something relating to cosine and math but i could not come to a conclusion. This is for an asteroid program and has to be able to rotate for the ship to move around the panel.