Everything you need to know about Identifiers in Java

Identifiers in Java is a very important aspect of Programming. They are mainly used for Identification Purposes. Following pointers will be covered in this article,

• Sample of Java Identifier
• Rules for defining Identifiers in Java
• Legal Variable Names
• Invalid Variable Names
• Reserved words in Java

The name given to a package, interface, class, method or a variable is known as a java identifier. In simpler terms, it can be defined as identification through symbolic names.

Let’s take a look at an example for a better understanding:

Sample of Identifiers in Java

public class A
{
    public static void main(String[] args)
    {
        int s = 18;
    }
}

In the above code, five identifiers are present as such:

• A: The class name defined by the user.
• main: The name of the method.
• String: Class name that is predefined in java.
• args: The name of a variable.
• s: Variable name.

Rules for defining Identifiers in Java:

• The characters that are allowed for identifiers are limited to all the alphanumeric characters ([A-Z],[a-z],[0-9]), ‘$‘(dollar sign) and ‘_‘ (underscore). For example, “edureka@” is an invalid name as a special character “@” is present in it.

• The identifiers should not begin with digits ([0-9]). For example, “123edureka” is invalid.

• Identifiers in java are case sensitive.

• While there is no such limit on the length of an identifier, programmers are advised to use an appropriate length of 4-15 letters.

• It must be noted that Reserved Words should not be used as identifiers. For example, “int while = 18” is invalid in java, as while is a reserved word.

• No white space must be given while defining a variable name.

• All the variable names are case-sensitive.

Legal Variable Names:

MyVariable
MYVARIABLE
myvariable
x
i
_myvariable
$myvariable
sum_of_numbers
edureka123

Invalid Variable Names:

My Variable // contains a white space
456edureka // Begins with a digit
c+d // plus sign is not an alphanumeric character
variable-5 // hyphen is not an alphanumeric character
add_&_sub // ampersand is not an alphanumeric character

Reserved words in Java:

To represent certain functionalities, java reserves some words. These words are known as reserved words. They cannot be used as identifiers as they are already used by the java syntax.
Reserved Words can be differentiated into keywords (50) and literals(3). While the functionality is defined by a keyword, the value is defined by a literal.

Identifiers are a necessity as they make the program readable and efficient.

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