What Are Identifiers in Java?

A name that “identifies” either a singular thing or a particular class of objects can be an idea, a countable physical object, or a physical uncountable substance. For in-depth understanding, read the full blog.

Introduction to Java Identifiers

A program’s basic building blocks are variables, methods, and classes. There is no use in writing a program if it does not include class, process, and variable. To declare a variable, we first say its data type and then its name.

In the same way, each programming language has its own set of rules and constraints that must be adhered to when writing code. The Java programming language’s identifiers also specify a few restrictions. The named identifiers in a program can be used to locate specific items.

Identifiers in the Java language

It’s a string of characters that identifies anything. An identifier is nothing more than a word or a single letter in our software. For an identifier to be valid, it must be named according to the requirements. Otherwise, the compiler will throw an error.

An identifier’s initial character is crucial for any coder to grasp, and the initial character of the identification is what drives the validation.

Which of the following symbol can be used in identifiers?

Letters (A-Z, a-z, and $) are permitted at the beginning of Java identifiers. No special symbols or numbers other than these characters can be used at the beginning of identification. Identifiers can be declared using any combination of numeric digits (0–9), alphabetic letters (A–Z, a–z), underscores (_), and spaces ($).

A Guide to Java’s Identifier Definition Rules

It is essential to keep in mind a few rules when declaring any Java identifier. Similarly, these criteria are relevant to C and C programming languages.

Characters ([A-Z], [a-z], [0-9]), the dollar sign ($), and the underscore (“_”)) can be used as the initial character in an identifier. An identifier can begin with numbers in Java and include digits (0-9), as long as they’re not the initial character of the identifier.

For example, the variable name “jigsaw#” is illegal because it contains the unique character “#,” which is not permitted in the identifier according to the rules of the Java coding language.

  • In addition, the identifiers should not start with digits ([0-9]).
  • To give you an idea, the phrase “123jigsaw” is not acceptable.
  • The identification can be any length. It is still recommended that they be used between 4 and 15 letters in length.
  • Java does not encourage using the two new keywords (goto and const) out of the 51 total. We can’t use any of these 49 keywords as identifiers. We will get an error if we utilise the keywords as IDs.
  • Some reserved keywords are public, import, short, try, new, switch, final, extends, class, and so on.
  • A line like an int try = five will result in an error because “try” is a non-existing identifier.

When defining an identity, there should be no white space. White space between identifiers is not supported in the Java programming language. A variable with the name “jig saw” is the answer to “find an invalid java identifier”.

The Java programming language distinguishes between uppercase and lowercase letters in the declaration of all variables. For example, variables named “Myvar” and “myvar” are not the same thing at all.Java is case-sensitive, and therefore uppercase and lowercase characters are treated differently.Java identifiers can be used.

What would it be like to live in a world without names? If you couldn’t call anything by its name, think about how you would have to describe a person or thing’s physical characteristics every time you referenced it. How would your phone’s contacts appear if they were nameless?

As in everyday life, naming is crucial in computer languages, and Java’s identifiers play a role in this. Just as giving people names makes it easier to identify them, Java identifiers allow programmers to refer to different program parts.

In Java, identifiers are defined:

Java employs identifiers, which are character strings, to distinguish between objects in programs. A name is provided to a class, variable, package, function, or interface, allowing the programmer to refer to that specific item from any location within the program.

In other words, a Java identifier is simply a word or character string used in a Java application. However, a legitimate identification must be given a name that follows set rules. In this regard, it is crucial to remember that the first character in the basic identifier is of a title indicates its legitimacy and is very significant.

The Java programming language supports the underscore (_), dollar symbol ($), and letters as the first character in the basic identifier are of an identifier (A-Z, a-z). No other distinctive sign or character may be used to start an identification besides these marks. Java supports the declaration of identifiers after the first character in the basic identifier is using the underscore (_), dollar sign ($), digits (0–9), and letters (A–Z, a–z). We’ll go through several standards for Java IDs in the following section.

Java Identifier Naming: Syntax

Like every language has laws governing how to form sentences from words and phrases, Java identifiers must follow precise guidelines to be accepted. The following is a list of the rules you must adhere to while defining identifiers in Java:

As identifiers, you can use any letter (A-Z, a-z), the dollar sign ($), or the underscore (_) as the first character in the basic identifier is and the valid identifiers in java.

Java identifiers can be defined by Java letters or Java digits, which are acceptable letters and numbers.

For instance, because it contains the prohibited unique character (#), the Java identity “jigsaw#” is not a legal identifier in java.

Only characters other than the first (0–9) in Java identifiers may be used. To put it another way, the initial character of a name can only be a letter, underscore, or dollar sign. Only those that come after the first character are allowed to be digits.

For instance, “56jigsaw” is not an acceptable identity because it starts with a digit. However, “jigsaw56” is a real one.

Java letters and numbers can be created using the Unicode character set, which supports most presently used writing scripts, including sizable Japanese, Chinese, and Korean sets.

White space shouldn’t be present in an identification. Spaces are not allowed in identifiers, so an underscore (_) can be used in their place.

The Java identifier “jig saw,” for instance, is wrong. Only the legal identifiers in java must be used.

The identifier is advised to stay within the ideal range of 4 to 15 characters, which can be any length.

The 49 reserved keywords for Java cannot be used as identifiers. These are some: switch, new, if, else, void, continue, class, import, etc. Using the reserved keywords as identifiers will result in a compilation fault.

The declaration of identifiers also considers the case because Java treats upper and lowercase letters differently.

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Examples of Java Valid Identifiers

A few instances of improper Java identifiers:

Those identifiers that do not meet the above-mentioned requirements are regarded as invalid. Here are some examples of wrong Java IDs.

123test (invalid because it starts with a digit)

The concept of identifiers is crucial to Java programming. They allow programmers to refer to specific pieces from anywhere in the code and serve as names for classes, variables, packages, methods, and interfaces. In other terms, Java identifiers are alphanumeric or alphabetic names given to classes, variables, methods, packages, constants, etc.


However, Java’s definition of identifiers demands adherence to a set of requirements; otherwise, the identifier would be invalid and give rise to a compile-time error. Additionally, there are several naming conventions for Java IDs. These are optional and do not require strict adherence. However, they simplify the code and more precisely convey the function and significance of identifiers. You can learn the various components of the Java programing language by enrolling on an online program. UNext offers Java courses for students to help them master these important concepts.

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