Polymorphism
  - Depends on the actual object. 
 
  - If x refers to a bank account, calls BankAccount.getMeasure
 
  - If x refers to a coin, calls Coin.getMeasure
 
  - Polymorphism (many shapes): Behavior can vary depending on the actual type of an object
 
  - Called late binding: resolved at runtime
 
  - Different from overloading; overloading is resolved by the compiler (early binding)