what is a constant?

Constants are very much like a variable in java. It’s a placeholder in memory that holds a value that is assigned to it  but the twist here is that the value will never be changed.  Example of a constant in java.

class example
{
    public static void main (String[]args)
  {
   int number1 = 2;
   final int FOOO = 100;
   System.out.println("The complete answer is" + (number1 + FOOO));
  }
}

by convention in java constants tend to be all in capital letters. For example FOO is the the constant that I used as i would if it was a variable by adding it to the int number1.

So when will you ever see a constant?
A rule of thumb for this is if you find your self declaring a set of variables that are never changing more than likely they should be constants.