CODEWITHSUNDEEP
javamethods
Ustaz Mohammed
Ustaz Mohammed

Reputation: 41

How nested method call works

Can anybody explain this how this line of code works:

Rational sum = a.add(b).add(c);

I don't understand how object b (which is an argument) is receiving a method?

Upvotes: 1

Views: 3459

Answers (2)

AllTooSir
AllTooSir

Reputation: 49372

This is called method chaining. The method add() actually returns a reference of the currently modified object or a new object of the same type on which the method was invoked. Say suppose the object referred to by a is a BigInteger , when you invoke a.add(b) , it returns a BigInteger object whose value is a+b , and hence you can invoke .add(c) on that object again.

 Rational sum = a.add(b).add(c);
 // is equivalent to
 Rational temp = a.add(b);
 Rational sum = temp.add(c);

Method chaining is not required. It only potentially improves readability and reduces the amount of source code. It is the core concept behind building a fluent interface.

A sample illustration:

enter image description here

This practice is used mostly in Builder pattern, you can find this pattern in API itself in StringBuilder class.

I don't understand how object b (which is an argument) is receiving a method?

No your understanding is wrong , a.add(b) means you are invoking method add() on object a and passing it a reference of object b . The resultant object which the method a.add(b) returns is of the same type as a , and then in succession you call the method .add(c) on the returned object passing a reference of object c to that method.

Upvotes: 4

Suresh Atta
Suresh Atta

Reputation: 121998

Its fluent chaining

Each method in the chain has to return a class or an interface. The next method in the chain has to be a part of the returned class.

in your case a.add(b) returning some calss/interface and then calling add(c) on that and that method returns your sum

Upvotes: 1

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