java程序设计教程(第六版)课后习题答案(19)

}

class FillFrame extends JFrame

{

public FillFrame()

{

setTitle("FillTest");

setSize(400,400);

// add panel to frame

DrawPanel panel = new DrawPanel();

add(panel);

}

}

class DrawPanel extends JPanel implements Runnable

{

private Thread t;

private int k=0;

public DrawPanel(){

setBackground(Color.white);

t = new Thread(this);

t.start();

}

public void paintComponent(Graphics g)

{

super.paintComponent(g);

Graphics2D g2 = (Graphics2D) g;

double xCenter=getWidth()/2;//中心点x

double yCenter=getHeight()/2;//中心点y

double radius=(int)(getWidth()*0.4);//半径

Ellipse2D circle = new Ellipse2D.Double(xCenter-radius,yCenter-radius,2*radius,2*radius); g2.draw(circle);

//画一个风车

for(int i=0;i<4;i++)

{

Arc2D arc1=new Arc2D.Double(xCenter-radius,yCenter-radius,2*radius,2*radius,-30+90*i+30*k,30,Arc2D.PIE);

g2.setPaint(Color.RED);

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