Arc2D.Float定义float 精度、端点闭合的弧
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Arc2D;

public class MainClass extends Frame {
public static void main(String[] args) {
(new MainClass()).setVisible(true);
}

public MainClass() {
super("Shape Sampler");
setSize(400, 550);
}

public void paint(Graphics g) {
Graphics2D g2d = (Graphics2D) g;

Arc2D arc = new Arc2D.Float(200, 50, 100, 50, 0, 90, Arc2D.CHORD);
g2d.draw(arc);

}
}
重点代码：new Arc2D.Float(200, 50, 100, 50, 0, 90, Arc2D.CHORD);
CHORD 闭合类型，用于通过从弧段的起始点到弧段的结束点画一条直线来闭合的弧。