找不到或无法加载主类HelloWorldAPP?

/* package book.code.ch1;*/

public class HelloWorldApp

{

public static void main (String args[ ])

{

System.out.println("Hello World!");

}

}

E:\android\javasrc\src\book\code\ch1>set classpath

CLASSPATH=.;D:\Program Files\Java\jdk1.8.0_31\lib;D:\Program Files\Java\jdk1.8.0

_31\lib\tools.jar;D:\Program Files\Java\jdk1.8.0_31\lib\dt.jar

最后排查，竟然是package book.code.ch1;惹的错

E:\android\javasrc\src\book\code\ch1>java HelloWorldApp

错误: 找不到或无法加载主类 HelloWorldApp

E:\android\javasrc\src\book\code\ch1>javac HelloWorldApp.java

E:\android\javasrc\src\book\code\ch1>java HelloWorldApp

Hello World!