javamail的邮件接收程序为什么总出一个错，帮帮忙啊！

该插入路径的包已经都导入了，有activiation.jar,mailapi.jar和pop3.jar;程序也没什么错，我用myeclipse7.0做的，可是还是一运行就有下面的提示：

 

Messages's length: 3
======================
Exception in thread "main" java.lang.NoClassDefFoundError: com/sun/mail/util/SharedByteArrayInputStream
 at com.sun.mail.pop3.Protocol.multilineCommand(Protocol.java:359)
 at com.sun.mail.pop3.Protocol.top(Protocol.java:253)
 at com.sun.mail.pop3.POP3Message.loadHeaders(POP3Message.java:433)
 at com.sun.mail.pop3.POP3Message.getHeader(POP3Message.java:256)
 at javax.mail.internet.MimeMessage.getSubject(MimeMessage.java:717)
 at wyh1.receive.getSubject(receive.java:104)
 at wyh1.receive.main(receive.java:352)