public class MyButton extends JButton 
{ 
    public MyButton() { 
    }

    public void paintComponent(Graphics g) { 
       super.paintComponent(g);
        g.drawArc(0,0,20,20);//可以自己绘制
    }
}

------解决方案--------------------
下面是swing里面自带的改表变外观的:

UIManager.setLookAndFeel(new LookAndFeel());  
JFrame.setDefaultLookAndFeelDecorated(true);  
JDialog.setDefaultLookAndFeelDecorated(true);  


还有就是一个项目做了一个提供流行的外观(look&feel)

一些好看的look and feel


.Substance  
这个项目的目的是提供一个流行的外观（look & feel）。这个外观（look & feel）联合了Windows XP和MacOS 10.4最好的特性并且需要JDK 5.0以上  

将下列jar文件拷贝到你的程序的classpath中，然后将下列代码段加入到你main函数中  
http://l1.edn.cn/cache/http/index.php?q=http%3A%2F%2F210.42.106.102%2Fbbs%2Fviewthread.php%3Ftid%3D111%26amp%3Bextra%3Dpage%253D1  
（注，其实我在别的文章中给出了一个例子，参见用java打造任意形状窗口一文中的的代码）  
1.substance look and feel:  
try {  
UIManager.setLookAndFeel(new SubstanceLookAndFeel());  
UIManager.put("swing.boldMetal", false);  
if (System.getProperty("substancelaf.useDecorations") == null) {  
JFrame.setDefaultLookAndFeelDecorated(true);  
JDialog.setDefaultLookAndFeelDecorated(true);  
}  
System.setProperty("sun.awt.noerasebackground", "true");  
SubstanceLookAndFeel.setCurrentTheme(new SubstanceLightAquaTheme());//设置当前的主题风格，同样我 们还可以设置当前的按钮形状，水印风格等等  
} catch (Exception e) {  
System.err.println("Oops! Something went wrong!");  
}  


2.smooth look and feel  
try {  
UIManager.setLookAndFeel(new SmoothLookAndFeel());  
UIManager.put("swing.boldMetal", false);  
} catch (Exception e) {  
System.err.println("Oops! Something went wrong!");  
}  


3. office/winxp/VisualStudio 2005 look and feel  
try {  
UIManager.setLookAndFeel("org.fife.plaf.Office2003.Office2003LookAndFeel");  
//UIManager.setLookAndFeel("org.fife.plaf.OfficeXP.OfficeXPLookAndFeel");  
//UIManager.setLookAndFeel("org.fife.plaf.VisualStudio2005.VisualStudio2005LookAndFeel");  
UIManager.put("swing.boldMetal", false);  
} catch (Exception e) {  
System.err.println("Oops! Something went wrong!");  
}


参考资料：http://www.blogjava.net/dyerac/archive/2006/04/03/38986.html


------解决方案--------------------
C/C++ code
Java绘制自定义按钮, 写了三种情况的， 当然还有其他的， 可以参考一下， 其实主要就是paintComponent和一些细节：

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Test01 {

    public static void main(String args[]) {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300,
                300);

        JPanel panel = new JPanel();
        JButton button = new MyButton2("Button");
        button.setFocusable(false);
        button.setBorderPainted(false);
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                System.out.println("Button is clicked");
            }
        });
        panel.add(button);
        frame.getContentPane().add(panel);

        frame.setVisible(true);
    }
}

class MyButton2 extends JButton {
    private static final long serialVersionUID = 1965063150601339314L;

    public MyButton2(String text) {
        super(text);
        setOpaque(false);
        setContentAreaFilled(false); // 这一句非常重要, 否则父类还会绘制按钮的区域.
    }

    @Override
    protected void paintComponent(Graphics g) {
        int width = this.getWidth();
        int height = this.getHeight();

        Graphics2D g2d = (Graphics2D) g;

        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);

        g2d.setColor(Color.GRAY);
        g2d.fillRoundRect(0,
                0,
                width,
                height,
                20,
                20);

        super.paintComponent(g); // 最后调用这个方法, 让父类绘制在按钮上绘制文字.
    }
}


Blur一个按钮:

class MyButton2 extends JButton {
    private static final long serialVersionUID = 1965063150601339314L;

    public MyButton2(String text) {
        super(text);
        // setOpaque(false);
        // setContentAreaFilled(false); // 这一句非常重要, 否则父类还会绘制按钮的区域.
    }

    @Override
    protected void paintComponent(Graphics g) {
        BufferedImage buf = new BufferedImage(getWidth(), getHeight(),
                BufferedImage.TYPE_INT_RGB);
        super.paintComponent(buf.getGraphics());

        float[] my_kernel = { 0.10f, 0.10f, 0.10f, 0.10f, 0.20f, 0.10f, 0.10f,
                0.10f, 0.10f };
        
        ConvolveOp op = new ConvolveOp(new Kernel(3, 3, my_kernel));
        Image img = op.filter(buf,
                null);
        g.drawImage(img,
                0,
                0,
                null);
    }
}


class ImageButton extends JButton {
    private static final long serialVersionUID = 1965063150601339314L;
    Image image = new ImageIcon("v4.png").getImage();

    public ImageButton(String text) {
        super(text);
        setOpaque(false);
        setFocusable(false);
        setBorderPainted(false);

        this.setPreferredSize(new Dimension(image.getWidth(this), image
                .getHeight(this)));
    }

    @Override
    protected void paintComponent(Graphics g) {
        g.drawImage(image,
                0,
                0,
                null);
    }
}