How to access outer class variable using inner static class object

Question

I'm studying inner classes in java. I have seen that if inner class is non static then it can easily access the outer class variable. But what if inner class is static, then how can we take a access of outer class's variable using static's class object ?

Below is my code, where am accessing outer class variable from inner class

package org;

public class Outerclass {

     String name = "Europe";

    public String getname() {

        return name;
    }

    public void setname(String name) {

        this.name = name;
        System.out.println(this.name);
    }

    static class innerclass {

        void updatename() {
            Outerclass o = new Outerclass();
            o.setname("USA");
        }

    }

    public static void main(String[] args) {
        Outerclass b = new Outerclass();
        b.name; // why this error here ? "Syntax error, insert "VariableDeclarators" to complete LocalVariableDeclaration"

        innerclass i = new innerclass();
        i.updatename();

    }

}

Instead of showing us how you're trying to do something (and failing) why won't you explain what is it you're trying to achieve ? — Nir Alfasi
– Nir Alfasi, Commented Oct 28, 2017 at 16:25

Nisal Edu · Accepted Answer · 2017-10-28 16:53:30Z

2

You can't access non-static contents inside the static content

When we create static inner class by default it will created as a outer template as a association of inner template. So we can load both together but only static things can be inside the static inner class.

Now there are no connection between objects of the classes. But there are connection between the templates.

Following is your code I have done some modification might help you

public class Demo {

     String name = "Europe";

    public String getname() {

        return name;
    }

    public void setname(String name) {

        this.name = name;
        System.out.println(this.name);
    }

    static class innerclass {

        void updatename() {
            Demo o = new Demo();
            o.setname("USA");
        }

    }

    public static void main(String[] args) {
        Demo b = new Demo();
        String a = b.name; // why this error here ? "Syntax error, insert "VariableDeclarators" to complete LocalVariableDeclaration"

        System.out.println(a);

        innerclass i = new innerclass();
        i.updatename();

    }

}

edited Oct 28, 2017 at 16:53

answered Oct 28, 2017 at 16:18

Nisal Edu

7,6294 gold badges32 silver badges38 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Javastudent Over a year ago

what if outer class's variable is static ?

Nisal Edu Over a year ago

static things can be accessed

Javastudent Over a year ago

Can you please explain how it can be accessed ?

Nisal Edu Over a year ago

make this modification static String name = "Europe";

Beri · Accepted Answer · 2017-10-28 16:48:43Z

0

Inner static class behives same as normal class:

can access static property/method of outer class
can't non-access static / methods of outre class directly, they will require an outerclass instance reference to do so.
it does not rquire an instance of outer class to be created

It is used mostly in two scenarios:

you are creating a group of classes with similar nature/function, and you want to keep them under one 'Napespace'
you want to create a private class that will not be visible to anyone, except to outter class (private static inner class). That way you can create interface implementations visible only to your outer class.

Non-static inner class:

it requires instance of outer class to be created
it can access methods and properties of outer class.

Quote:

...inner classes can access all members of the declaring class, even private members. In fact, the inner class itself is said to be a member of the class; therefore, following the rules of object-oriented engineering, it should have access to all members of the class.

edited Oct 28, 2017 at 16:48

answered Oct 28, 2017 at 16:24

Beri

11.6k4 gold badges38 silver badges59 bronze badges

4 Comments

Javastudent Over a year ago

what if outer class's variable is static ?

Beri Over a year ago

You can access them

Shubhendu Pramanik Over a year ago

@Beri regarding can't access static / methods of outre class directly, they will require an outerclass instance reference to do so.. I think you can access static methods without instance of outer class.

Beri Over a year ago

True, I have forgotten to add non keyword.Thank you for the comment.

Collectives™ on Stack Overflow

How to access outer class variable using inner static class object

2 Answers 2

4 Comments

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

4 Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related