Q:

Accessing directly a method in a class from its object

if a class has only one method which is not called may times but rarely, then instead of calling the method in a traditional way as below 
RarelyCalledClass orarelyCalled = new RarelyCalledClass();
orarelyCalled.rarelyCalledMethod();

can i call this as below.
(new RarelyCalledClass()).rarelyCalledMethod();

Will this increase the performance as compiler has to do less operation.

A:

It will be exactly the same performance and code. Just that you can't access the instance anymore in your code.. And the readability is also worse (in my and most peoples opinion).
Also something you always should keep in mind: Premature micro optimization is evil.
Profile your application. Is this an actual bottleneck? No? Then don't bother.

