Have to throw out that disclosure ð. While there are a number of essential oils you can use for minor migraines and head pain, two of the top single oils are Peppermint and Lavender. Peppermint is effective for helping to relieve minor symptoms of those mind-numbing headaches that come from a variety of culprits.
An abstract class is like a class, but differs in that it only defines generic methods in the class, but does not actually implement them. Those methods will be implemented later by specialized sub-classes. This is how we get interfaces - interfaces are the implementation of the abstract class.
A class can extend one other class and implement any number of interfaces. An interface can extend any number of interfaces. When a class implements an interface it implements all of the methods declared in that interface. You can have variables and parameters of an interface type. method in Java that has a parameter of interface type is nearly the same as a function template in C++. A class that uses interfaces to type any variables or parameters behaves very similarly to a class template in C++. Just think of the interface names as if they were template arguments.