Naming conventions

Core Java · lesson 19 of 42 · 3 min read

Use the names the whole ecosystem expects, so your code reads like the standard library.

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Key points

  • Classes, records, interfaces and enums are UpperCamelCase nouns: CustomerOrder.
  • Methods and variables are lowerCamelCase, and a method name starts with a verb: findById.
  • static final constants are UPPER_SNAKE_CASE: MAX_LOGIN_ATTEMPTS.
  • Packages are all lower case with no underscores, usually a reversed domain: com.acme.orders.
  • Boolean methods read as a question: isEmpty(), hasNext(). Avoid data and temp.
  • None of this is enforced by the compiler, but every tool, reviewer and library assumes it.

Example

public class Main {

    static final int MAX_LOGIN_ATTEMPTS = 3;

    enum OrderStatus { NEW, SHIPPED, CANCELLED }

    record CustomerOrder(String customerName, int itemCount) {}

    static boolean isShippable(CustomerOrder order) {
        return order.itemCount() > 0;
    }

    public static void main(String[] args) {
        CustomerOrder pendingOrder = new CustomerOrder("Ada", 3);

        System.out.println("class / record -> CustomerOrder : " + pendingOrder);
        System.out.println("variable       -> pendingOrder  : " + pendingOrder.customerName());
        System.out.println("method verb    -> isShippable() : " + isShippable(pendingOrder));
        System.out.println("constant       -> MAX_LOGIN_ATTEMPTS = " + MAX_LOGIN_ATTEMPTS);
        System.out.println("enum constant  -> " + OrderStatus.SHIPPED);
        System.out.println("package        -> com.acme.orders, all lower case");

        System.out.println("names are the cheapest documentation you will ever write");
    }
}

Follow the conventions and your code stops needing an explanation.

Comments and Javadoc The ternary operator

This is a reading copy. The full lesson — with the visual explainer, the interactive lab and a Run button for the code — lives in the Core Java course, and every lesson in it is listed on the Core Java contents page.