About Java grammar: Is it 'class.method.method'?

Question

I'm learning Spring framework with a tutorial online. However, I have a question about this Java code:

     attributes.addFlashAttribute(ResultMessages.success().add(
             ResultMessage.fromText("Created successfully!")));
     return "redirect:/todo/list";

Full source

What I'm wondering about: Is it 'Class.method.method'? If so, how can it be possible?

why do you think its not possible. can you be a bit explanatory? — Vikas Prasad, Oct 27 '17 at 07:20
If you ask this kind of question, you should not use Spring yet. Please learn the Java basics and look at the soure code of Spring. — Turing85, Oct 27 '17 at 07:22
@LCL , you are not defining a method, you are calling on. not on the method itself, but on what it returns. just take a look at the answer I've posted, it gives an example of what happens. — Stultuske, Oct 27 '17 at 07:29
Possible duplicate of [how to achieve method chaining in java?](https://stackoverflow.com/questions/21180269/how-to-achieve-method-chaining-in-java) — Lino, Oct 27 '17 at 07:29

score 7 · Answer 1 · edited Oct 27 '17 at 07:22

7

It's called chaining. the second method is called upon the returned value of the first.

let's say this:

public Person {
  private String name;
  public Person(String name){ this.name = name; }

  public String getName() { return this.name; }
}

if you have an instance p of Person, the next two snippets are the same (in result)

String pN = p.getName().toUpperCase();

and:

   String name = p.getName();
   String pN = name.toUpperCase();

edited Oct 27 '17 at 07:22

Arnaud

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answered Oct 27 '17 at 07:21

Stultuske

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@Berger nice catch ;) – Stultuske Oct 27 '17 at 07:23
And chaining can also be done with array indexing: `name.toUpperCase().toCharArray()[0].toLowerCase()`. – Joop Eggen Oct 27 '17 at 07:30
Thank you for giving me a perfect example :D – LCL Oct 30 '17 at 06:17

Anastasios Vlasopoulos · Accepted Answer · 2017-10-27T07:54:27.317

1

This is called method chaining or named parameter idiom and it is a syntax for invoking multiple method calls. This is a common feature on many object oriented languages.

Simply speaking, by this syntax you directly invoke a method on the returned value without the need of assignment to a variable object first. One major advantage is the reduction of vertical problem in programming.

edited Oct 27 '17 at 07:54

answered Oct 27 '17 at 07:47

Anastasios Vlasopoulos

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Thank you! Your explanation is the simplest and the most understandable :) – LCL Oct 30 '17 at 06:15

About Java grammar: Is it 'class.method.method'?

2 Answers2