PracticeInterface

// Interface Class 
package javaapplication1;

import java.util.ArrayList;

public interface In1 {
   final static ArrayList<Integer> arrli = new ArrayList<Integer>();
}

//first class 
package javaapplication1;

import java.util.ArrayList;


public class JavaApplication1 implements In1 {

    
    public static void main(String[] args)  {
     
        arrli.add(1);
        arrli.add(2);
        
    } 
              
    
}


//second class 

package javaapplication1;

public class NewClass implements In1{
    
    public static void main(String[] args)  {

        arrli.add(3);

    } 
}

//third class

package javaapplication1;

import static javaapplication1.In1.arrli;

public class NewClass1 extends NewClass {
        public static void main(String[] args)  {
       
        
        arrli.add(4);
        for(int i=0; i<arrli.size(); i++)
        {
            System.out.println(arrli.get(i));
        }
    } 
        
}