Java Identifier,,,

Identifiers are names we give to our variables, constants, classes, and methods.
Identifiers is token to word presntation.

Identifiers must comply with these rules:

* The first character of an identifier must be a letter, an underscore(_), or a dollar sign($).
* The rest of the characters in the identifier can be a letter, underscore, dollar sign, or digit. Note that spaces are NOT allowed in identifiers.
* Identifiers are case-sensitive. This means that age and Age are different identifiers.
* Identifiers cannot match any of Java's reserved words.

Although not required, we strongly recommend that you name your identifiers using Java naming conventions.

Examples:
These identifiers are valid:

MyClass
$amount
$change
username
user_name
_sys_var1
totalGrades;
TotalGrades;
one
zero

And These identifiers are NOT valid:

My Class // spaces are not allowed
numberOf*s // the asterisk cannot be used
final // final is a reserved word
1Way // identifiers cannot start with a digit