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Naming variables

Learn camelCase and valid naming rules.

Naming variables

Java variable names use camelCase: the first word starts lowercase, the following words start uppercase. Example: studentGrade, totalPrice.

Naming rules:

  • Can contain letters, digits, $, _
  • Cannot start with a digit
  • Cannot contain spaces
  • Reserved keywords (class, int) are not allowed

Descriptive names make code more readable.

Practice Define a camelCase variable

Write a Main class with a main method. Assign 85 to int studentGrade. Print it with println.

Sample solution

Main.java
public class Main {
    public static void main(String[] args) {
        int studentGrade = 85;
        System.out.println(studentGrade);
    }
}

Expected output

85

Naming tips

A good variable name clearly says what it holds. Avoid vague names like x or data. Names like userCount, totalAmount are descriptive.

English names make the code easier to share internationally. Non-ASCII letters are technically allowed but not recommended.

Abbreviations should be consistent: either always cnt or always count. Mixing hurts readability.

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Which is a valid variable name?

  • 1number
  • number-grade
  • class
  • studentGrade Correct answer

Explanation: studentGrade is camelCase and not a keyword.

2 Match the naming conventions

Term Meaning
camelCase Variable
PascalCase Class
ALL_CAPS Constant
snake_case Not Java

3 Complete the camelCase variable

Question 
int ____ = 90;
Answer 
int studentGrade = 90;

Explanation: studentGrade is a camelCase variable name.

All lessons in Beginner

1 Java basics

  1. What is Java?
  2. The main method
  3. Comments
  4. Class skeleton
  5. javac and java
  6. Summary - Java basics

2 Variables

  1. int and double
  2. boolean
  3. String
  4. Naming variables
  5. final variables
  6. Summary - Variables

3 Data types

  1. Primitive types
  2. Type casting
  3. String concatenation
  4. Math class
  5. BigInteger and BigDecimal
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add/subtract
  3. Multiply/divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic
  2. Comparison
  3. Logical
  4. Bitwise
  5. Assignment and increment
  6. Summary - Operators

6 String basics

  1. length and charAt
  2. equals and equalsIgnoreCase
  3. indexOf and substring
  4. toUpperCase and trim
  5. String.format
  6. Summary - String basics

7 Conditionals

  1. The if statement
  2. else and else if
  3. Nested if
  4. switch
  5. Ternary
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. do-while
  4. break and continue
  5. for-each
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Updating quantity
  5. Putting it together

10 Arrays

  1. Declaring arrays
  2. Array access
  3. Filling arrays
  4. Multi-dimensional arrays
  5. Copying arrays
  6. Summary - Arrays

11 Array methods

  1. Arrays.sort
  2. Arrays.toString
  3. Arrays.binarySearch
  4. Arrays.copyOf
  5. Arrays.fill
  6. Summary - Array methods

12 Collections

  1. ArrayList
  2. add and get
  3. HashMap
  4. put and get
  5. HashSet
  6. Summary - Collections

13 Methods

  1. Defining methods
  2. return
  3. void methods
  4. Method overloading
  5. Scope
  6. Summary - Methods

14 Method parameters

  1. Primitive parameters
  2. Object parameters
  3. varargs
  4. Multiple values via array
  5. final parameters
  6. Summary - Method parameters

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 String builder

  1. StringBuilder
  2. append
  3. insert and delete
  4. reverse
  5. toString
  6. Summary - String builder

17 Input and output

  1. Scanner
  2. nextInt and nextLine
  3. System.out.printf
  4. BufferedReader
  5. try-with-resources
  6. Summary - Input and output

18 Enum

  1. Declaring enums
  2. values and valueOf
  3. Enum fields
  4. Enum methods
  5. switch with enum
  6. Summary - Enum

19 Exception basics

  1. try/catch
  2. finally
  3. throw
  4. Exception hierarchy
  5. Multiple catch
  6. Summary - Exception basics

20 Beginner final

  1. Project design
  2. Data model
  3. Business logic
  4. Error handling
  5. Putting it together