Identifiers and Keywords
Identifiers are used to name Java language entities. They begin with a Unicode letter, underscore character (_), or dollar sign ($). Subsequent characters consist of these characters and the digits 09. Identifiers are case sensitive and cannot be the same as a reserved word or the boolean values True or False or the null value. Avoid using the dollar sign character; it is intended for use by compiler-generated identifiers.
Know Your Java-Reserved Words
It is a good idea to memorize this list because you are likely to seeat least one exam-related question that requires knowledge of the preceding keywords. Also, remember that null, true, and false are literal values and not reserved keywords.
The following are examples of valid Java identifiers:
The following are invalid Java identifiers:
The following words are reserved by the Java language and cannot be used as identifiers: