Three characteristics of object-oriented

1. Package: Public Private protected

2. Inheritance: Extends

3, polymorphism: A variety of state food category {Fish meat, bone class} animal class {cat, dog} cat eats fish dog eats bone

4. Overriding: Subclasses and parent classes new attributes of subclasses override attributes of the parent class

5, Abstract class: A method is not sure to declare this method is abstract public function cry (); If the class contains an abstract method, the class must declare the class abstract class

Role: Other classes inherit from him and implement their methods

Note: Abstract classes cannot be instantiated, a class inherits an abstract class, and it must implement all the abstract methods of this abstract class (unless the class is also an abstract class)

Three characteristics of object-oriented