Variables

Section 1 - Keywords

A keyword is one of the words used to define the syntax of the Java programming language. The following are a few examples of Java keywords:

class public static void

Section 2 - Identifiers

An identifier is a valid name. Java defines the following rules for identifiers:

• The first character must be an uppercase or lowercase letter, $, or _
• Subsequent characters must be an uppercase or lowercase letter, $, _, or a digit
• Identifiers may not contain punctuation or whitespace
• Identifiers may not be the same as a keyword
• There is no limit to the length of a Java identifier

The following are examples of valid Java identifiers:

        hello1                

        $mother        

        _father                

        BaBy                

        hello_world        

The following are examples of invalid Java identifiers:

        1hello                (identifier may not begin with a digit)

        hello world        (identifier may not contain whitespace)

        hello;world        (identifier may not contain punctuation)

Java is a case sensitive language: baby, BABY, and BaBy are three different identifiers.