How to make this code working?

Question

This code comes from challenges, and I am not Java programmer so I ask somebody who is. I just want minor changes on this to make it working, thanks!

public class Program
{
interface P{
void print(int x);
}
class Main implements P{
void print(int x){
System.out.print(x);
}
}
public static void main(String[] args) {
P ob = new Main();
ob.print(10);
}
}

Answer 1

1)make print() method inside Main class as public
2)use the reference of Program class to create the object of Main class because objects of non-static nested class can be created only with the reference of outer class

public class Program
{
interface P{void print(int x);}
class Main implements P
{
public void print(int x)
{
System.out.println(x);
}
}
public static void main(String args[])
{
Program ref=new Program();
Main ob = ref.new Main();
ob.print(10);
}
}