Character Set:
It is a set of symbols which are used to write a Java Program.
Examples:
A to Z
a to z
0 to 9
Special Symbols ( ) [ ] { } + - & % ….
Keyword:
it is a reserve word which has some pre-define meanings.
Identifiers or User Define words:
In programming languages, identifiers are used for identification purposes. In Java, an identifier can be a class name, method name, variable name, or label.
Rules of Identifiers or User Defined words:
• Keywords cannot be used as identifiers
• Identifiers must not start with any numeric or it is always recommended to start some of the identifiers with small case.
• It must not contain any special symbol other that (_) or $.
• Identifiers must not contain any blank space in between.