3.7 Class Variables and Methods
1. Exam Points
Access class variables or methods using a class name.Access instance variables or methods using an instance name.The value of final variables(constants) can not be changed.- If you want to
count how many objects of a class is created, use a static variable.(Ex. static int count)
2. Knowledge Points
(1) Class Variables and Methods
Class variables and methods are declared using the static keyword.Class variables belong to the class, with all objects of a class sharing it. (ex. pi is shared by all circles)Class variables or methods can be accessed by external classes using the class name.If you want to count number of objects created for a class, make the count variable static.- Example:
Class methods from the same class can access class variables and class methods directly without creating an object. 
(2) Final Variables
When a variable is declared final, its value cannot be modified.- Example: final int x = 10;
- The value of x can not be changed since it is declared as final
- It is recommended to name a final variable using uppercase.
- Example: final int ERROR_CODE = 404;
3. Exercises
