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Ok, so I am revisiting java after many years and I was just trying out some random program when I found out that I was having an error in the following snippet. Can someone give me any heads on how to solve this? I know that static methods will not be able to access non static variables but I created an instance for it right? Also I am not getting any heads on reading some other questions so try to help me.

 import java.io.*;
    public class phone
    {
        int x=6;
        int getx()//I also tried using this function but everything in vain
        {
            return x;
        }
    }
    public class Testing_inheritance extends phone
    {
        public static void main (String args[])throws IOException
        {   
            phone xy=new phone();
            int y=phone.x;
            y+=10;
            System.out.println("The value of x is " +y);
        }
    }
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  • 1
    int y=phone.x; should probably be int y=xy.x;. Commented May 15, 2017 at 10:02
  • Next time please attach console outoput. Commented May 15, 2017 at 10:05

3 Answers 3

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3

You probably intended to access the instance variable of the instance you created :

        phone xy = new phone();
        int y = xy.x;

Since x is not a static variable it can't be accessed without specifying an instance of the phone class.

Of course this will also fail, unless you change the access level of x to public (which is possible but not advisable - you should use getter and setter methods instead of directly manipulating instance variables from outside the class).

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6 Comments

Dude, both things work while using static variables and in this case it is more meaning full to use phone.x since it is a class variable
and if I do xy.x I am getting the errror : The public type phone must be defined in its own file
@IshanSrivastava But x is not a static variable, so you cannot use phone.x.
@IshanSrivastava That's an unrelated error, and it speaks for itself. Each public class must be in a separate file would name is ClassName.java.
Ok thanks, sorry I got a bit confused over there on whats static and whats not.
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1

x is not static. You need to access it through an object reference.

Do 

int y = xy.getx(); //could do xy.x, but better to access through method

Also, it's better to stick with Java naming conventions

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0

Almost there, I made small but very important changes, I hope you get this otherwise just ask ;-)

Phone.java

public class Phone //<--- class with capital letter always
{
    int x=6;
    int getx()//I also tried using this function but everything in vain
    {
        return x;
    }
}

Testing_inheritance.java

import java.io.*;

    public class Testing_inheritance extends Phone
    {
        public static void main (String args[])throws IOException
        {   
            Phone xy=new Phone();
            int y= xy.getx(); //<--- principle of encapsulation
            y+=10;
            System.out.println("The value of x is " +y);
        }
    }

OR private inner class :

  import java.io.IOException;

public class Phone {
    int x = 6;

    int getx()// I also tried using this function but everything in vain
    {
        return x;
    }

    private static class Testing_inheritance extends Phone {
        public static void main(String args[]) throws IOException {
            Phone xy = new Phone();
            int y = xy.getx();
            y += 10;
            System.out.println("The value of x is " + y);
        }

    }
}
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1 Comment

exactly, otherwise it should be a private class, as you can notice I separate this in two classes, Phone.java and Testing_inheritance.java, you should do the same or declare as private class

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