No parentheses in java

Question

I am learning Java and I have learned that methods use parentheses for passing parameters. However, I have also noticed that sometimes I see code which to me looks like a method but it does not have parentheses.

MyObject.something()

MyObject.somethingElse

Where somethingElse does not have parentheses. I assume this is similar to how an arrayList has the size method for getting its size:

myList.size()

whereas an array has length to get its size, which does not have parentheses:

myArray.length

Is my assumption correct? If not, what is the difference? This is probably an elementary question, but because of the amount of words I need to explain this problem, I have had trouble searching for it.

Answer 1

somethingElse is a property (data member), not a method. No code in the class is run when you access that member, unlike with a method where code in the class is run.

Here's an example:

public class Foo {

    public int bar;

    public Foo() {
        this.bar = 42;
    }

    public int getBlarg() {
        // code here runs when you call this method
        return 67;
    }

}

If you create a Foo object:

Foo f = new Foo();

...you can access the property bar without parens:

System.out.println(f.bar);        // "42"

...and you can call the method getBlarg using parens:

System.out.println(f.getBlarg()); // "67"

When you call getBlarg, the code in the getBlarg method runs. This is fundamentally different from accessing the data member foo.

Answer 2

it is a class field which isn't a private field (usually it can be protected,package or public), so you can take it straight from your class. Usually fields are private, so you cannot take it like this outside your class definition.

Answer 3

myList.size() call a method defined in list class (public defined)

myArray.length call a property in array class not method

public class MyClass{

    public int length;

    public int size(){
    ....
    }
}

MyClass mc =new MyClass();
mc.length;
mc.size();

Answer 4

This is triggering method called something of the instantiated object called someObject.

someObject.something();

This is accessing a property of the object called someObject (property which is public, most probably).

someObject.name