Variable Names

Variable names, and identifiers in general, have to follow a few rules in Java. You can find these rules at the end of this page, but we'll summarize them here:

  • You cannot use a [Java keyword]( https://docs.oracle.com/javase/tutorial/java/nutsandbolts/_keywords.html as an identifier.
  • An identifier can only contain letters (uppercase or lowercase), numbers, the underscore character (_), or the dollar sign ($) character.
  • An identifier cannot begin with a number.
  • Identifiers are case-sensitive, which means thisname and thisName are different identifiers even though they look nearly the same.

There are also some optional rules that you should follow with identifiers. These rules are only optional in the sense that your code can technically run if you break these rules, but your code will be harder to read and much more likely to contain errors if you don't follow them.

  • Java variable names should follow the lower camel case naming convention. This means all variable names should start with a lowercase letter, contain no underscores or dollar signs, and each word after the first should start with an uppercase letter. For example thisVariableNameIsUsingLowerCamelCase, although in practice you don't want your variable names to be that long. This is important because most other Java code (including the standard library code you will be using in your own programs) is written this way, and not following this convention will make the names in your code inconsistent and easy to mix up.
  • Don't create two identifiers that are the same except for capitalization. This is confusing and makes it easy to accidentally use the wrong identifier.
  • Whenever possible, give your variables descriptive names. If a variable has some inherent meaning (such as a variable that stores a person's name), then use a name that will tell the reader what that meaning is. For example, a variable that stores someone's age could be called age, and a variable that stores a person's name could be called name. This makes it much easier to understand your code.