eclipse 错误 hierarchy of the type is inconsiste

在看开源代码的时候，总是碰到eclipse 报这个错误：
eclipse 报错the hierarchy of the type  is inconsiste

1.root cause
These errors happend because some interface
/class in the hierarchy cannot be resolve.
For example: the error is occur in your class - class x, x inherits y, and in turn, y inherits z. However, the compiler cannot resolve z (in above error is EventManager), because z is belong to a library that is not included.
Therefore, you have to add package containing z to the classpath/ or project's Java Build Path (if you are using eclipse).
 
2. 解决方案：如果你写的类A 继承了 B 而B 继承 C,如果接口c或类C不在你所引的jar 包中,就报此信息,导入jar 包即可