2. After the first character, identifiers can contain any combination of letters, currency characters, connecting characters, or numbers.
3. In practice, there is no limit to the number of characters an identifier cancontain.
5. Identifiers in Java are case-sensitive; so pen and PEN are two different identifiers.
Some of the legal identifiers are:
$aturn, _$23, _23, $_aturn, there_is_no_limit_to_the_number_of_characters
Some illegal identifiers are:
23$, -saturn, :saturn, saturn#, .saturn
If you have any questions...let them come through the comments, I will gladly answer each one of them.