南京金熊电器有限公司:java的package问题，急需回答

代码如下：
package beantest;

public class mybean{

public mybean(){System.out.print("aaa");};

public static void main(String a[]){
new beantest.mybean();
}
}

编译好后放在beantest文件夹
然后在cmd中进入运行 d:\beantest java mybean
下面的错误：请问为什么，怎么解决
java.lang.NoClassDefFoundError: mybean (wrong name: beantest/mybean)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:539)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:251)
at java.net.URLClassLoader.access$100(URLClassLoader.java:55)
at java.net.URLClassLoader$1.run(URLClassLoader.java:194)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:187)
at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274)
at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
Exception in thread "main"