Why use named constants:    PI !!

  

public class MyProg
{
    public static void main(String[] args)
    {
       double PI = 3.14158265358979;
       double radius = 2;
       double area;

       PI = 6.1;   // accidents can happen

       area = PI * radius * radius;
   }
}

Problem:    we can accidentally change the constant PI      (by: PI = .... later in the program)

How to define named constants:    use the final keyword

The keyword final will disallow assigning a value to a variable: 

public class demo
{
    public static void main(String[] args)
    {
       final double PI = 3.14158265358979;
       double radius = 2;
       double area;

       PI = 6.1;       // Compile error

       area = PI * radius * radius;
   }
}

DEMO: demo/02-elem-prog/08-final/demo.java

Naming convention used by Java programmers

  

Naming convention:

   Class Name:      MyClass     ("Camel case" with first upper case letter)
   Method name:     myMethod    ("Camel case" with first lower case letter)
   Variable name:   myVariable  ("Camel case" with first lower case letter)
   Constant:        PI          (All CAPS)



public class MyProg  
{
   public static void main(String[] args) 
   {
       final double PI = 3.14158265358979;  
       double radiusOfCircle = 2;   
       double areaOfCircle;

       area = PI * radius * radius;
   }
}