Identifiers
All Java variables must be identified with unique names .
These unique names are called identifiers .
Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume).
Note
It is recommended to use descriptive names in order to create understandable and maintainable code:
// Good int minutesPerHour = 60;
// OK, but not so easy to understand what m actually is int m = 60;The general rules for naming variables are:
- Names can contain letters, digits, underscores, and dollar signs
- Names must begin with a letter
- Names should start with a lowercase letter, and cannot contain whitespace
- Names can also begin with $ and _
- Names are case-sensitive ("myVar" and "myvar" are different variables)
- Reserved words (like Java keywords, such as int or boolean ) cannot be used as names
Invalid Identifiers
Here are some examples of invalid identifiers that would cause errors:
Example
// Invalid identifiers: int 2ndNumber = 5; // Cannot start with a digit int my var = 10; // Cannot contain spaces int int = 20; // Cannot use reserved keywords