About Question enthuware.ocpjp.i.v11.2.1495 :

[Deleted User 6318]

In this case, only the first "a" will be removed.

In which case? There is no case here with removing any "a".

Also the space in remove(Object ) could be removed.

[admin]

Right, the line starting wit "In this case..." should be removed.
Space after object is fine because this is how a method signature is written conventionally.

thank you for your feedback!