FSDataInputStreamWrapper unbuffer can NOT invoke the classes that NOT implements CanUnbuffer but its parents class implements CanUnbuffer

FSDataInputStreamWrapper unbuffer can NOT invoke the classes that NOT implements CanUnbuffer but its parents class implements CanUnbuffer

For example:

There are 1 interface I1 and one class implements I1 named PC1 and the class C1 extends from PC1

If we want to invoke the C1 unbuffer() method the FSDataInputStreamWrapper unbuffer  can NOT do that.