JAVA基础代码分享--求圆面积

问题描述

　　用户输入圆的半径，计算并显示圆的面积

代码分享

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

    /**
     * 计算圆的面积
     */
    public static void main(String[] args) {
        System.out.print("请输入圆的半径：");
        Scanner in = new Scanner(System.in);
        r = in.nextDouble();
        m = Math.PI*r*r;
        System.out.println("圆的面积是："+m);
        EventQueue.invokeLater(new Runnable() {//事物分配线程，进行显示窗口
            @Override
            public void run() {
                JFrame frame = new SimpleFrame();
                frame.setTitle("求圆面积");//设置窗口的左上角标题
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//设置关闭窗口事件
                Toolkit kit = Toolkit.getDefaultToolkit();
                Dimension screenSize = kit.getScreenSize();
                int screenWidth = screenSize.width;//获取屏幕的宽度
                int screenhHeight = screenSize.height;//获取屏幕的长度
                frame.setLocation(screenWidth/2-250, screenhHeight/2-100);//设置窗口在屏幕上的显示位置
                Image image = new ImageIcon("Image/image.png").getImage();//设置窗口的左上角图标
                frame.setIconImage(image);
                frame.setVisible(true);//启动显示窗口
            }
        });
    }

}

//设计窗口
class SimpleFrame extends JFrame{
    private static final int DEFAULT_WIDTH = 300;
    private static final int DEFAULT_HEIGHE = 200;
    public SimpleFrame(){
        add(new NotHelloWordComponent());//将文本填充到窗口
        pack();//调整窗口大小
//        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHE);//设置窗口的大小
    }
}

//在窗口中显示文本信息
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("半径为："+new Circle().r+"的圆，面积为："+new Circle().m, MESSAGE_X, MESSAG_Y);//在窗口中显示文字
    }
    @Override
    public Dimension getPreferredSize() {
        return new Dimension(DEFAULT_WIDTH, DEFAULT_HEIGHE);//返回组件的首选大小
    }
}