The purpose of polymorphism

- [Instructor] We're looking at four classes here. … Ireland and Brazil that extend country, … and United Nations that I'm using to interact with them. … Because all these countries have the same parent, … you can treat them as though they were of the same type. … I'll show you that working. … 'Kay. … They all have a dance method. … So I'm going to make them dance together. … First I'm going to make a list containing the countries. … Then I'm going to iterate through the list. … Then I'm going to call the dance method on each one. … Because each of the countries … at least have the dance method, … even if they had overridden it in their own special way, … they still have a default version in the parent country. … So I can treat them all as if they were of the same type. … Now all this talk of dancing doesn't sound all that serious, … but imagine if you were building a system … that had to process a number of credit cards … in different ways. … This pattern might lend itself to that. …