Object-oriented overview,

Object-oriented overview,

This topic explains what object orientation is, What are local and member variables, object-oriented features, how to create and use objects.

Object-oriented

Object-oriented is relative to process-oriented:

Both object-oriented and process-oriented thinking:

Process-oriented:

It emphasizes functional behavior:

Object-oriented:

Encapsulate functions into gold objects, emphasizing functional objects;

Object-oriented is based on process-oriented;

Concepts of objects and classes:

1. The object uses computer language to describe the things in the problem domain. The object uses "attributes" and "methods" to correspond to the static and dynamic attributes of the things respectively.

2. A class is an abstract concept used to describe objects of the same class shape. The class defines the static and dynamic attributes of such objects;

 

Object-oriented features:

1. encapsulation (encapsulation );

2. inheritance (inheritance );

3. polymorphism (polymorphism );

Class Definition

Describing things in life is nothing more than describing the properties and methods of things:

For example, a person has attributes such as height and weight, and has behaviors such as speaking and playing:

The same is true for describing things using classes in Java:

Attribute: member variables in the corresponding class:

Behavior: member functions (methods) in the corresponding class );

Differences between member variables and local variables:

1. member variables:

1): member variables are defined in the class and can be accessed throughout the class;

2) member variables are created with the object and exist in the heap memory where the object is located:

3) member variables have default initialization values;

2. Local variables:

1) local variables are defined only within the local range, for example, within the function and within the statement;

2) local variables exist in the stack memory;

3) The function range ends and the variable space is automatically released;

4) No Default initialization value for local variables;

Create an object. Use the following object:

Class Car {

String color = "red ";

Int num = 4;

Void show (){

System. out. println ("color =" + color + ". num" + num );

}

}

Class CarDemo {

Public static void main (String [] args ){

Car c = new Car (); // create an object

C. color = "black"; // modify the object field

C. show (); // use the object function

}

}

Anonymous object

Anonymous objects are simplified objects.

Two usage cases of anonymous objects:

1) when the object method is called only once;

2) Anonymous objects can be passed as actual parameters;