java - 无法找到或加载主类cmd

Question

我用 javac 编译了一些示例代码，当我尝试运行它时，我得到的是:

C:\Users\Lenis>cd C:\Java\2D

C:\Java\2D>java donut.board
Error: Could not find or load main class donut.board

我尝试编写“java -cp . donut.board”，但仍然得到相同的结果。

我的类路径是:“C:\Program Files\Java\jdk1.7.0_02\lib\tools.jar;。”

如何解决？

这是代码:

package donut;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.geom.Ellipse2D;
import javax.swing.JPanel;

public class Board extends JPanel{

public void paint(Graphics g)
{
  super.paint(g);

  Graphics2D g2 = (Graphics2D) g;

  RenderingHints rh =
        new RenderingHints(RenderingHints.KEY_ANTIALIASING,
                           RenderingHints.VALUE_ANTIALIAS_ON);

  rh.put(RenderingHints.KEY_RENDERING,
         RenderingHints.VALUE_RENDER_QUALITY);

  g2.setRenderingHints(rh);

  Dimension size = getSize();
  double w = size.getWidth();
  double h = size.getHeight();

  Ellipse2D e = new Ellipse2D.Double(0, 0, 80, 130);
  g2.setStroke(new BasicStroke(1));
  g2.setColor(Color.gray);


  for (double deg = 0; deg < 360; deg += 5) {
      AffineTransform at =
          AffineTransform.getTranslateInstance(w / 2, h / 2);
      at.rotate(Math.toRadians(deg));
      g2.draw(at.createTransformedShape(e));
    }
}
}

Answer 1

类中没有 main 方法，并且在调用时必须给出 donut.Board(大写 B)，它区分大小写。添加主要方法。