@LarsChung : code is attached below:
public abstract class Person
{
public void buyFood(String foodName, int payment)
{
System.out.println("Buy " + foodName + " and pay $" + payment + ".");
pay(payment);
}
public abstract void pay(int amt);
}
public class Visitor extends Person
{
@Override
public void pay(int amount)
{
money_v -= amount;
System.out.println(this.to_s() + " has got HK$" + money_v + "left.");
}
}