java - why no reference variable used to add method in awt -

i going through awt first time in java, found how create button in creating object button - instance b1 - , add component container using add method [add(b1)] . in case noticed was, add() method of parent class may container has been inherited, , button b1 directly added without having reference calling method add() ( .add() ) , petty confusing me. how method called without using dot operator?

if method belongs object in, either directly or through inheritance parent, don't have prefix method anything. can use

add(); 

if want clear, can use this keyword specify method belongs object in. work same above:

this.add();