为什么会有错： ------------------------------程序--------------------------------

import java.awt.Graphics;

calss Box{

double width;

double height;

double depth;

}

class BoxDemo extends java.applet.Applet

{public void paint(Graphics g)

{Box myBox=new Box();

double volume;

myBox.width=10;

myBox.height=20;

myBox.depth=15;

volume=myBox.width*myBox.height*myBox.depth;

g.drawString("the volume"+volume,25,50);

}

} ---------------------------------------------------------------------------------- 错误提示：

C:\>javac box.java

box.java:2: 'class' or 'interface' expected

calss Box{ ^ ---------------------------------------------------------------------- 请问大吓们什么原因啊！~~真的救命。一点搞不懂后面的也不好搞懂！~~ 真诚希望能帮我一下！~~~