CODEWITHSUNDEEP
javastaticjava.lang.class
Deep Roy
Deep Roy

Reputation: 89

Can we access static members and static functions of a class with the help of instance variables of that class in java?

To illustrate the contrast. Look at the following java snippet:

public class Janerio {
    public static void main(String[] args) {
        new Janerio().enemy();
    }

    public static void enemy() {
        System.out.println("Launch an attack");
    }
}

The above code works very fine and seems to be yes as answer to this question as the output turns to be as follows.

Launch an attack

But at the very next moment when I run the following snippet

public class Janerio {
    public static void main(String[] args) {
        System.out.println(new Janerio().class);
    }
}

I get the compile time error

/Janerio.java:3: error: <identifier> expected
System.out.println(new Janerio().class);}
                                 ^
/Janerio.java:3: error: ';' expected
    System.out.println(new Janerio().class);}
                                          ^
2 errors

I don't see why such a situation comes up because in the previous snippet I was able to access the static "enemy" function with the help of an instance of the class but here it's proving false. I mean why can't I access the ".class" static method with the help of the instance of the class. Am I wrong to consider ".class" to be a static function or member of the class Janerio and is it wrong to be analogous to the static features of both the snippets? But as soon as I call the ".class" with the class name things appear to be that ".class" is static in nature but it deviates to the be static on calling ".class" with an instance of the class.

public class Janerio {
    public static void main(String[] args) {
        System.out.println(Janerio.class);
    }
}

Output we get:

class Janerio

Upvotes: -2

Views: 212

Answers (4)

Przemysław Moskal
Przemysław Moskal

Reputation: 3609

Yes, you can access these static members of classes that way, but the better practise is to use name of that class instead of the name of specific referece to object of that class. It makes your code clearer to understand and to read as static members of class do not belong to specific object but to whole class. For example:

class MyClass {
    static int count = 0;
}

It is better to access this field that way:

MyClass.field = 128;

instead of changing that value using the name of specific reference, for example:

MyClass obj1 = new MyClass();
MyClass obj2 = new MyClass();
obj1.field = 128;

Because it can be confusing when you realize that this way even obj2.field has assigned new value of 128. It might look a bit tricky, so again, I would suggest the first presented method of calling methods or changing values assigned to fields.

Upvotes: 0

Trigary
Trigary

Reputation: 431

Am I wrong to consider ".class" to be a static function or member of the class Janerio?

Yes, it's not a variable and it's definitely not a method. You have to use the Object#getClass method when you want to get the class of an instance.

Upvotes: 0

Joop Eggen
Joop Eggen

Reputation: 109567

With .class you do not select a field (besides class is a keyword).

It is a pseudo operation, usable with a class name, yielding a Class instance:

int.class, Integer.class, java.util.List.class

Upvotes: 0

Ayo K
Ayo K

Reputation: 1774

.class references the Class object that represents the given class. it is used when there isn't an instance variable of the class. Hence it doesn't apply to your usage

Read more here: https://docs.oracle.com/javase/specs/jls/se8/html/jls-15.html#jls-15.8.2

Upvotes: 1

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