jbutton设置边框为圆角矩形

您可以使用下面这段代码来设置JButton的边框为圆角矩形：

jbutton.setBorder(new RoundBorder(20));

其中，RoundBorder是自定义的一个类，代码如下：

import java.awt.*;
import java.awt.geom.*;
import javax.swing.border.*;

public class RoundBorder implements Border {
    
    private int radius;

    public RoundBorder(int radius) {
        this.radius = radius;
    }

    public Insets getBorderInsets(Component c) {
        return new Insets(this.radius + 1, this.radius + 1, this.radius + 2, this.radius);
    }

    public boolean isBorderOpaque() {
        return true;
    }

    public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setColor(c.getBackground());
        g2.fill(new RoundRectangle2D.Double(x, y, width - 1, height - 1, radius, radius));
        g2.setColor(c.getForeground());
        g2.draw(new RoundRectangle2D.Double(x, y, width - 1, height - 1, radius, radius));
    }
}

这样，您就可以把JButton的边框设置为圆角矩形了。