Keywords in Java are also known as reserved words, are already defined in Java with a predefined meaning. These words cannot be used with variables or object name.
Example of using integer Keyword:
int number = 5;
List of Keywords used in Java are shown in the table:
Identifier is the symbolic name given to the variables name, class name, method name, etc for identification reason so that the program can identify them throughout the program. The name is given by the user with their choice but by following naming rules.
These rules are:
- An identifier cannot be a Java keyword.
- Identifiers are case sensitive, that temp and Temp are different identifiers.
- Identifiers must begin with a sequence of letters(A-Z, a-z) and digits(0-9), $ or _. Note that an identifier cannot have the first letter as a digit.
- Whitespaces are not allowed.
- Also symbol like @, #, and so on cannot be used.
Example of some valid identifiers are:
Here are some invalid identifiers: