Inheritance

  class Set
  {
    protected int n1,n2;
    public void setData(int x,int y)
    {
        n1=x;
        n2=y;
    }
    public int sum()
    {
        int s=n1+n2;
        return s;
    }
    public double mean()
    {
        double m=sum()/2.0;
        return m;
    }
  }
  class XSet extends Set
  {
    protected int n3;
    public void setData(int x,int y,int z)
    {
        setData(x,y);
        n3=z;
    }
    public int sum()
    {
        int s=super.sum()+n3;
        return s;
    }
    public double mean()
    {
        double m=sum()/3.0;
        return m;
    }
  }
  class demo
  {
    public static void main(String args[])
    {
        Set a = new Set();
        a.setData(4,5 );
        System.out.println("Sum of set a is "+a.sum());
        System.out.println("Mean of set a is "+a.mean());
        XSet b=new XSet();
        b.setData(1,2,4);
        System.out.println("Sum of set b is "+b.sum());
        System.out.println("Mean of set b is "+ b.mean());
    }
  }

  class person
  {
    private String name,city;
    public void setData(String nm,String ct)
    {
        name=nm;
        city=ct;
    }
    public void showData()
    {
        System.out.println("Name is "+name);
        System.out.println("City is "+city);
    }
  }
  class student extends person
  {
    private int rollno;
    public void setData(int rn,string nm,String ct)
    {
        setData(nm,ct);
        rollno=rn;
    }
    public void showData()
    {
        System.out.println("RollNo is "+rollno);
        super.showData();
    }
  }
  class demo
  {
    public static void main(String args[])
    {
        Person a =new Person();
        a.setData("Amit","Amravati");
        a.showData();
        student b=new student();
        b.setData(4117,"Nitin","Nagpur");
        b.showData();
    }
  }