As part of new test development for the CSR : JDK-8196350
It's been observed that specification mismatch to the behavior.

 java.io.Reader
Specification :
  nullReader()

 "While the stream is open, the read(), read(char[]), read(char[], int, int), read(Charbuffer), ready()), skip(long), and transferTo() methods all behave as if end of stream has been reached. After the stream has been closed, these methods all throw IOException."
 
 Actual result :
 invoking ready() after closing the nullReader does not throw IOException.
 
2. "The mark() method does nothing, and the reset() method throws IOException."

  Actual Result :
 Invoking the mark() throws IOException.

Code snipped attached to demonstrate this.