import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.JPanel;


public class Circle extends JPanel{
    public int value;

    public Circle(){
        
    }
    public Circle(int value){
        this.value = value;
    }
    public int getValue(){
        return value;
    }
    
    public void setValue(int value){
        this.value = value;
        repaint();
    }
    
    
    protected void paintComponent(Graphics g){
        super.paintComponent(g);
        int clockRadius = (int)(Math.min(getWidth(), getHeight())*0.8*0.5);
        int xCenter = getWidth()/2;
        int yCenter = getHeight()/2;
        g.setColor(Color.RED);
        g.drawOval(xCenter-clockRadius, yCenter-clockRadius, 2*clockRadius, 2*clockRadius);
        
        int line1 = (int)(clockRadius);
        int line1X = (int) (xCenter-clockRadius*Math.cos(value*(2*Math.PI/60)));
        int line1Y = yCenter+value;
        g.drawLine(xCenter, yCenter, line1X, line1Y);
        
    }
    public Dimension getPreferredSize() {
        return new Dimension(100,100);
    }
    
}

    public static void main(String[] args) throws Exception {
        JFrame app = new JFrame("测试");
        app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        app.setSize(400, 500);
        Circle panel = new Circle(20);
        app.add(panel);
        app.setVisible(true);
        for(int i = 0;i<100;i++)
        {
            Thread.sleep(100);
            panel.setValue(20 + i*5);
        }
    }