JAVA基礎代碼分享--求圓面積

問題描述

 　　用戶輸入圓的半徑，計算並顯示圓的面積

代碼分享

/**
 * @author hpu-gs
 * 2015/11/25
 */
public class Circle {
    public static Double r;
    public static Double m;

    /**
     * 計算圓的面積
     */
    public static void main(String[] args) {
        System.out.print("請輸入圓的半徑：");
        Scanner in = new Scanner(System.in);
        r = in.nextDouble();
        m = Math.PI*r*r;
        System.out.println("圓的面積是："+m);
        EventQueue.invokeLater(new Runnable() {//事物分配線程，進行顯示窗口
            @Override
            public void run() {
                JFrame frame = new SimpleFrame();
                frame.setTitle("求圓面積");//設置窗口的左上角標題
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//設置關閉窗口事件
                Toolkit kit = Toolkit.getDefaultToolkit();
                Dimension screenSize = kit.getScreenSize();
                int screenWidth = screenSize.width;//獲取屏幕的寬度
                int screenhHeight = screenSize.height;//獲取屏幕的長度
                frame.setLocation(screenWidth/2-250, screenhHeight/2-100);//設置窗口在屏幕上的顯示位置
                Image image = new ImageIcon("Image/image.png").getImage();//設置窗口的左上角圖標
                frame.setIconImage(image);
                frame.setVisible(true);//啟動顯示窗口
            }
        });
    }
    
}

//設計窗口
class SimpleFrame extends JFrame{
    private static final int DEFAULT_WIDTH = 300;
    private static final int DEFAULT_HEIGHE = 200;
    public SimpleFrame(){
        add(new NotHelloWordComponent());//將文本填充到窗口
        pack();//調整窗口大小
//        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHE);//設置窗口的大小
    }
}

//在窗口中顯示文本信息
class NotHelloWordComponent extends JComponent{
    public static final int MESSAGE_X = 120;
    public static final int MESSAG_Y = 100;
    
    private static final int DEFAULT_WIDTH = 500;
    private static final int DEFAULT_HEIGHE = 200;
    public void paintComponent(Graphics g){
        g.drawString("半徑為："+new Circle().r+"的圓，面積為："+new Circle().m, MESSAGE_X, MESSAG_Y);//在窗口中顯示文字
    }
    @Override
    public Dimension getPreferredSize() {
        return new Dimension(DEFAULT_WIDTH, DEFAULT_HEIGHE);//返回組件的首選大小
    }
}