[Soumikbhat]

I've just started out on java programming and am stuck on this :

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
    public class A
    {
        int a;  char b;
        public A(int x, char y )
        {
	    a=x; b=y;
	}

        public void print()
        {
            System.out.println("Print function called");
        }

        public A()
        {
        }
    }

    public interface B
    {
	void unfriend();
    }	
    public class C extends A implements B
    {
	char d;
	public  C(int x, char y, char z)
        {
	    super(x,y);
            d=z;
	}

	@Override
	public void unfriend()
        {
	    System.out.println("unfriended");
	}
    }

    public static void main (String[] args) throws java.lang.Exception
    {	
        C s = new C(); //error line

	s.unfriend();
	// your code goes here
    }
}

The line marked as error line gives
error: non-static variable this cannot be referenced from a static context C s =new C();

I don't have much clue about this problem, so kindly throw some light on this and its workaround...

This post has been edited by xclite: 08 February 2015 - 12:31 PM
Reason for edit:: Made formatting consistent

[xclite]

Since the class C is a nested member of your class Ideone, it can't be referenced from a static context - your static context being the main method.

Make C static and it should stop giving you that error. For more information, see: http://docs.oracle.c...aOO/nested.html

Also, you'll notice after that that you aren't sending the correct parameters to C's constructor - you didn't get C a constructor which takes no arguments, yet you're calling it like you did.

[Soumikbhat]

xclite, on 08 February 2015 - 12:28 PM, said:

Since the class C is a nested member of your class Ideone, it can't be referenced from a static context - your static context being the main method.

Make C static and it should stop giving you that error. For more information, see: http://docs.oracle.c...aOO/nested.html

Also, you'll notice after that that you aren't sending the correct parameters to C's constructor - you didn't get C a constructor which takes no arguments, yet you're calling it like you did.

thank you for that...

I changed my code to

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{	public class A{
 int a;  char b;
     public A(int x, char y ){
	
	a=x; b=y;
		        }
        

      public void print() 
                        {
            System.out.println("Print function called")	;
                        }
         
      public A(){
	
                }

 }


public interface B{
	

           void unfriend();
}	


static public class C extends A implements B{
	char d;
	public  C(int x, char y, char z){
		super(x,y); //error line
		//this->d=z;
			d=z;
	}
	public C(){
		
	}
	@Override
	public void unfriend(){
		System.out.println("unfriended");
	}
	
}

	public static void main (String[] args) throws java.lang.Exception
	{	C s=new C(2,'a','b'); 
		
		
		s.unfriend();
		// your code goes here
	}
}

Now super(x,y) throws an error :
error: no enclosing instance of type Ideone is in scope
super(x,y);
The code can be viewed at http://ideone.com/oC8ent
Thanks...

This post has been edited by Soumikbhat: 08 February 2015 - 12:49 PM

[CasiOo]

Ugh you are making this harder and harder for yourself
Working with inner classes and static inner classes as a beginner is not a good idea at all

Make your life easy:
- Remove the static keyword again
- Move every class and interface out into its own file
This way you won't be having any inner classes, and the compiler will be happy

Read about inner classes when you're ready for it, but trust me, that shouldn't be your focus for quite some time

[xclite]

Good point - the reason I didn't suggest that was because they're working in Ideone, but inner classes are more rarely used than 1 class per file anyway.