Hello viewers, welcome to GeeksforGeeks. In
this tutorial we’ll learn about Java Identifiers.In programming languages, identifiers are used
for identification purpose. In Java an identifier can be a class name, method name, variable
name or a label. For example : Here test is the identifier for the class name and a is
the identifier for int variable.There are some rules for defining the java identifiers. The only allowed characters for identifiers
are all alphanumeric characters, which are these.For example “[email protected]” is not a valid
java identifier as it contain ‘@’ – special character. Identifiers should not start with digits([0-9]).
For example “123geeks” is a not a valid java identifier. Java identifiers are case-sensitive There is no limit on the length of the identifier
but it is advisable to use an optimum length of 4 – letters only. Reserved Words can’t be used as an identifier.
For example “int while=20;” is an invalid statement as while is a reserved word. There
are reserved words in Java.These are the examples of valid identifiers. The identifier can be
in camel case, all caps or all small letters. The identifier can be combination of alphabet
and a digit. It can have special characters which were specified in the last slide, thus
these all strings are a valid identifiers.These are the examples of invalid identifiers, the
first one contains space, thus its an invalid identifier. This begins with digits, thus
invalid. The remaining contains invalid special characters thus they are also invalid identifiers.There
are words which are reserved in java and you can not use them as an identifier. Out of
are keywords and 3 are Reserved literals. Reserved literal consists of true false and
null. Whereas keywords are further divided into two categories: used and unused. Used
words are if, else, for, etc. Unused words are const and go to. Thank you for watching!
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