The 8 parameters constructor's javadoc is read:
    IllegalArgumentException - if bufferSize or maxNotifs is less than 1
    NullPointerException - if delegate is null.

The 1 and 5 parameter(s) constructors javadoc are read:
    IllegalArgumentException - If delegate is null.

I didn't check if the implementation does exactly that but NPE isn't appropriate when delegate is null: IAE for all constructors seems the obvious way.