repaint(); ในภาษา JAVA คืออะไรเหรอค่ะ

พอดีว่า มาเจอคำว่า repaint; ใน JAVA เลย งง เลยคำว่าคืออะไร แล้ว ลองค้นดู ก็ไม่ค่อยมีใครพูดถึงและอธบายเยอะเท่าที่ควร
ขออนุญาต แสดงโคด นะค่ะเพื่อที่จะได้เข้าใจ จุดประสงค์มากขึ้น


import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
import javax.swing.*;
public class HittingRec extends JPanel implements ActionListener, MouseListener{
    // position, width, and height of a moving character
    Timer timer = new Timer(5000, this);
    int xPos = 0;
    int yPos = 0;
    int width = 40;
    int height = 40;
    int x=0;
    int y=0;
    // player’s scores
    int score = 0;
    HittingRec(){
        timer.start();
        addMouseListener(this);
    }
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        customDrawingMethod(g);
    }
    public void customDrawingMethod(Graphics g) {
        setBackground(Color.black);
        double w = (getSize()).getWidth();
        double h = (getSize()).getHeight();
        double r1 = Math.random();
        double r2 = Math.random();
        int midX = (int)(w*r1);
        int midY = (int)(h*r2);
        xPos = midX-width/2;
        yPos = midY-height/2;
        g.setColor(Color.white);
        g.fillRect (xPos, yPos, width, height); // head
        g.setColor (Color.black);
        g.fillOval (midX-10, midY-10, 5, 5); // left eye
        g.fillOval (midX+5, midY-10, 5, 5); // right eye
        g.drawArc (midX-10, midY, 20, 10, 190, 160); // smile
        g.setColor(Color.yellow);
        g.drawString("Hits = " + score, (int)(w-100), 20 );
}
    public static void main(String[] args) {
        JFrame frame = new JFrame("Hitting a Cartoon");
        frame.add(new HittingRec());
        frame.setSize(new java.awt.Dimension(600,400));
        frame.setVisible(true);
    }
    public void actionPerformed(ActionEvent e) {
        repaint();
    }
    public void mouseReleased(MouseEvent m){

    }
    public void mouseEntered(MouseEvent m){

    }
    public void mousePressed(MouseEvent m){
        x=m.getX();
        y=m.getY();
        if(x>=xPos&&y>=yPos&&x<=xPos+width&&y<=yPos+height){
            score++;
        }
        x=0;
        y=0;

    }
    public void mouseClicked(MouseEvent m){
    }
    public void mouseExited(MouseEvent m){

    }

}

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