Abstract methods: abstract is to add keywords, then remove the braces, ending direct semicolon.
Abstract class: abstract class where the method must be abstract class job. Before you can write the abstract class.
How to use abstract classes and abstract methods:
1. You can not create new abstract class object directly.
2. must inherit the abstract parent class with a subclass.
3. Subclasses must override the abstract parent class which covers all the abstract methods.
Overwrite (achieved): abstract subclass remove keywords abstract method, then fill the method body braces.
4. Create a subclass object for use.
note:
An abstract class may not contain abstract methods,
as long as an abstract method where the class is abstract, you can.
Such a method is not an abstract class is abstract and can not create object directly, there use in some special scenarios.