Java Identifiers

✅ Java Identifiers

In Java, identifiers are names given to variables, methods, classes, packages, or any user-defined items in a program.

Example identifiers in a program:

🧠 Rules for Java Identifiers

Identifiers must follow these rules:

Rule	Example
✔ Must start with a letter, underscore `_`, or dollar sign `$`	`name`, `_value`, `$price`
✔ Can contain letters, digits, underscores, and $	`age1`, `student_name`, `$totalAmount`
❌ Cannot start with a number	`1age` ❌
❌ Cannot contain special characters except `_` or `$`	`my-name`, `total#value` ❌
❌ Cannot be a Java keyword	`class`, `public`, `int` ❌

🏷 Java is Case Sensitive

Identifiers treat uppercase and lowercase letters differently.

Examples:

Here, value and Value are two different identifiers.

✨ Examples of Valid Identifiers

❌ Examples of Invalid Identifiers

Identifier	Reason
`2name`	Starts with a number
`student-name`	Contains `-` (not allowed)
`total amount`	Contains space
`class`	Reserved keyword

📌 Naming Conventions (Best Practice)

Not rules, but recommended by Java community:

Type	Convention	Example
Class Name	PascalCase	`EmployeeDetails`
Variable / Method	camelCase	`studentName`, `getSalary()`
Constant	UPPERCASE_WITH_UNDERSCORE	`MAX_SPEED`, `PI_VALUE`

✔ Example Program

class StudentDetails {
int studentAge = 20;
String studentName = "John";

public static void main(String[] args) {
StudentDetails obj = new StudentDetails();
System.out.println(obj.studentName);
System.out.println(obj.studentAge);
}
}

class StudentDetails {

int studentAge = 20;

String studentName = "John";

public static void main(String[] args) {

StudentDetails obj = new StudentDetails();

System.out.println(obj.studentName);

System.out.println(obj.studentAge);

}

Java Identifiers