Class variable, instance variable

 

1 ) Instance variables and class variables
Memory is allocated to instance variables of each object.;
Class variable (that is Static Variable)Allocate memory only when the first object is generated,All instance objects share the same class variable,Changes to class variables of each instance object will affect other instance objects..Class variables can be directly accessed by class names,You do not need to create an instance object, or you can use the Instance Object Sequence class variable.

The difference is:Class variables are shared by all objects, and one of them changes its value. Other objects get the changed result;WhileInstance variables are private objects. A certain object changes its value without affecting other objects;

Example:

Public Class {

Static int A = 0 ;//Class variable

Private int B = 0 ;//Strength Variable

}

Public Class B {

Public void main (string [] ARGs ){

A a1 = new ();

A a2 = new ();

A1.a = 3 ;//EquivalentA. A = 3;

A1. B = 4;

System. Out. println (a2.a );// Result: 3 ,Class variables are for all objects, so A1 Change A , A2 Of A Also changed

System. Out. println (a2. B );// Result: 0 , The instance only changes its own, so A1 Object B Change without affecting objects A2 Of B Variable

}}

2 ) Instance methods and class methods
The instance method can operate the instance variables of the current object, or the class variables. The instance method is called by the instance object.
HoweverClass MethodYou cannot access instance variables. You can only access instance variables.. Class methods can be called directly by class names,It can also be called by instance objects.Class methods cannot be used This Or Super Keyword.