Sometimes when programming, we want to create variables that never change.
In Java, you can use the keyword final to make sure that your variables can't be changed.
It is a programming convention to make static and final variables all capital letters so that they are easy to identify in your code.
EXAMPLE:
double pi = 3.14159265359;
pi = 7.7; // This is perfectly valid.
System.out.println(pi); // This prints out 7.7.
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final double PI = 3.14159265359; //notice we added "final"
PI = 7.7; //This will cause an error because PI had been labeled as final.
System.out.println(pi); // It still prints out 3.14159265359.