Question

I was looking at this piece of code and can not understand what the .add statement is doing (fromCity) and (toCity) is just Strings?

getDestinations(fromCity).add(toCity);

Method:

public ArrayList<String> getDestinations(String fromCity)

Answer 1

This is called chaining of method calls. You are invoking the next method on the return value of the previous method.

So, the getDestinations() method returns you a ArrayList, now instead of storing your returning value, you are invoking the add method of the ArrayList on the method call.

getDestinations(fromCity).add(toCity);

This is equivalent to: –

ArrayList<String> list = getDestination(fromCity) // returns `ArrayList - list`
list.add(toCity) // invoke `add` method on returned arraylist.

Similarly you can chain method calls upto any lavel: –

meth1(parameter1).meth2(param3).meth3(param3);