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Rules

Java is a case-sensitive language.

In a single program, the following variable names would all refer to different variables: 

number Number NUMBER NuMbEr

Rules for Naming Variables

The Java compiler will enforce rules for naming variables.

We only need to remember three rules for declaring legal variables: * The name must begin with a letter or $ or _. * Characters after the first character may also be numbers. * You can't use Java reserved words. These are words in the Java language's vocabulary that you are not allowed to use, like double or class.

Recommendations for Naming Variables

We also want to make sure that variables are useful to ourselves and other developers.

  • Name variables something that is related to their purpose. int age is much better than int x when we want a variable for storing how many years a person has been alive.
  • Use camel case, starting with a lowercase letter.

camel case

After the first word in a variable, the first letter of each concatenated word is capitalized. For example camelCase or bookIdentificationNumber.

Naming variables is slightly different than naming a class, as classes use camel case but start with a capital letter, like class VariableNaming.

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