Making Contact Management System

import java.lang.Math; // header stuff MUST go above the first class
import java.util.ArrayList; 

// our main class becomes a file but the main method is still found
public class ManagementSystem
{
  public static void main(String[] args)
  {
    //create ArrayList of Contact
    ArrayList<Contact> contacts = new ArrayList<Contact>();
    //create new contact
    Contact c = new Contact("Maciej");
    c.setContactNumber(contacts.size()+1);
    System.out.print(c + "\n");
    //add contact to the array of contacts
    contacts.add(c);
    
    //create another contact
    c = new Contact("Raja");
    c.setContactNumber(contacts.size()+1);
    System.out.print(c + "\n");
    //add 
    contacts.add(c);
    //remove Raja's contact from list
    contacts.remove(c);
    System.out.print("Contact 'Raja' has been removed \n");
    System.out.print("List of Contacts contains: " + contacts.size() + " element(s)\n");

  }
}
// this will become its own file too (and these can be in any order)
public class Contact
{
  private String sName = "";
  private int iNumber = 0;

  public Contact(String _Name)
  {
    sName = _Name;
  }

  public void setContactNumber(int _Number){
      iNumber = _Number;
  }
  
  public String toString()
  {
    return iNumber + " - " + sName;
  }
}

1 - Maciej
2 - Raja
Contact 'Raja' has been removed 
List of Contacts contains: 1 element(s)