Variable Rules

In Java, creating a variable is called declaring a variable. The Java programming language is statically-typed. This means all variables must be created(declared) before you can use them.

Variables are given names. The names of the variables are referred to as identifiers. They are rules and conventions to naming variables.

Identifier Naming Rules

1. All variable names must begin with a letter of the alphabet, an underscore, or a dollar sign.

   total
   _total
   $count
   

   Avoid starting your variable names with the "$" or "_" characters. While it's technically legal to begin your variable's name with "_", this practice is discouraged.

2. After the first initial letter, variable names may also contain letters, digits 0 to 9, $ and "_".

   __messages
   number2
   

   Conventions (and common sense) apply to this rule as well. Choose full and meaningful words that describe what the variable is being used for.

3. No spaces or special characters are allowed. The following are illegal variable names :

   2much
   #hashtag
   @username
   first name
   

4. The name can be of any length, but don't get carried away.

   thisisaverylongvariablebutitslegal
   

5. Variable names are case-sensitive. Uppercase characters are distinct from lowercase characters. Using ALL uppercase letters are primarily used to identify constant variables. These are two different variables :

   TOTAL
   total
   

6. You cannot use a Java keyword (reserved word) for a variable name.