I wonder what is happening in this Java code block

Question

Objectname.methodone()
.methodtwo()
.methodthree()
.methodfour();

Are these statements above same as

Objectname.methodone();
Objectname.methodtwo();
Objectname.methodthree();
Objectname.methodfour();

Thanks,

You may find this interesting: http://stackoverflow.com/questions/2872222/how-to-do-method-chaining-in-java-o-m1-m2-m3-m4 — Mudassir, Jan 23 '12 at 05:41

score 2 · Answer 1 · answered Jan 23 '12 at 05:32

It depends on the return types of methodone, methodtwo, methodthree and methodfour. What's going on is you're calling methodone on Objectname, methodtwo on the return type of methodone and so on.

If methodone through methodfour all return this, then yes, it would be the same.

This is referred to as method chaining.

score 1 · Answer 2 · answered Jan 23 '12 at 05:32

1

Probably, if the implementation of each of those methods ends with return this; so that the calls can be chained like that. But it's possible that each returns a reference to a different object, on which the "next" method is then called.

answered Jan 23 '12 at 05:32

Wyzard

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score 0 · Answer 3 · answered Jan 23 '12 at 05:30

no its not like that it is as

    Objectname.methodone().methodtwo().methodthree().methodfour();

similar to the

 result = method1().method2(). ........ method n()

its called method chaining

refer Method chaining in Java

EXAMPLE

class Person
{
        private final String name;
        private int age;

        public Person setName(final String name) {
                this.name = name;

                return this;
        }

        public Person setAge(final int AGE) {
                this.age = AGE;

                return this;
        }

        public void introduce() {
                System.out.println("Hello, my name is " + name + " and I am " + age + " years old.");
        }

        // Usage:
        public static void main(String[] args) {
                Person person = new Person();
                // Output of this sequence will be: Hello, my name is Peter and I am 21 years old.
                person.setName("Peter").setAge(21).introduce();
        }
}

source :- http://en.wikipedia.org/wiki/Method_chaining

score 0 · Answer 4 · answered Jan 23 '12 at 05:30

Not necessarily, methodtwo is called on the return value of methodone and methodthree is called on the return value of methodtwo and so on. They are not (necessarily) called on the same object.

The equivalent is:

MethodOneReturnType x = object.methodone();
MethodTwoReturnType y = x.methodtwo();
MethodThreeReturnType z = y.methodthree();

score 0 · Answer 5 · answered Jan 23 '12 at 05:30

0

It depends on what those methods return. methodtwo is being called on the return of methodone. if methodone returns Objectname, then they are the same.

answered Jan 23 '12 at 05:30

mowwwalker

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score 0 · Answer 6 · answered Jan 23 '12 at 05:35

it is very unlikely they'll be same. Think of a pizza builder.

new PizzaBuilder().withDough("dough").withSauce("sauce").withTopping("topping").build();

this builds the complete pizza. whereas if you call the with methods separately it will build only a partial pizza.

I wonder what is happening in this Java code block

6 Answers6