What does a period mean in a variable name?

Question

I saw this in my textbook and was wondering what it was and when to know to use it.

public class TV{
    public static final int MAX.VOLUME = 10; 
    public static final int DEFAULT.CHANNEL = 2;
    public static final int DEFAULT.VOLUME = 4;

Answer 1

In java, there are certain rules when defining a variable name.

A variable name must not ,

• be a java keyword
• contain spaces

The first character of a variable name,

• can be a character ( az|AZ )
• can be a dollar sign ( $ )
• can be a underscore ( _ )
• can not be a number ( 0-9 )

The rest of the name can contain any combination from the following,

• characters ( az|AZ )
• dollar signs ( $ )
• underscores ( _ )
• numbers ( 0-9 )

All variable names are case-sensitive .

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So using a period ( . ) in the middle of an variable name will result in a compile error.