201671010128 2017-09-10 "Java Programming" objects and classes

Several key concepts of programming to objects: Abstract data types, classes and objects, encapsulation, class hierarchies (subclasses), inheritance, polymorphism.

• A class is a conceptual model that defines all the attributes of an object and the actions required, and the class is the prototype of the object.
• An object is a concrete entity that exists, with clearly defined states and behaviors.

There are three main characteristics of the object:

1. Object behavior (behavior)--what actions can be applied to an object, or what methods can be applied to an object?
2. State of the object--how does the object respond when the method is applied?
3. Identity of an object--how do you identify different objects with the same behavior and state?

• all of them belong to the same class objects all have the same features and operations.
• In Java, the object is constructed and initialized with a constructor (constructor).
• A constructor is a special method in a class that has the same name as the class name.
• The relationships between classes:

1. Dependency (USES-A): If a method in one class operates on another class's object, then the class relies on another class.
2. Aggregation (HAS-A): An object of Class A contains an object of class B.
3. Inheritance (IS-A): Represents a relationship between a particular class and a generic class. In general, if Class A inherits Class B, then class A inherits not only the method and state of Class B, but also its own method and state.

2. Object-oriented Programming course learning progress bar

Moonphases	(read/write) Number of lines of code	Posted Blog Volume/Blog comments number	Classroom/after-school time (hours)	The most satisfying programming task
First week	20/7	1/1	6/4	Write the Hello World program
Second week	38/20	1/1	6/4	Experiment two task three
Third week	50/30	1/1	6/5	Experiment Three
Cumulative

201671010128 2017-09-10 "Java Programming" objects and classes