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static final

Learn to define constants with static final.

static final

A constant is a value that does not change throughout the program. In Java constants are defined with the static final keywords. static provides a single copy at the class level; final ensures the value cannot be changed.

Example: class Settings { static final int MAX_USERS = 100; }. Here MAX_USERS is a constant. It takes the value 100 when the class loads and cannot be changed afterwards. If you write Settings.MAX_USERS = 200; you get a compile error. Constants let you manage values used in multiple places from a single point. When the value changes, only the definition is updated; all usage points are automatically affected.

Why use constants?

Constants manage values used repeatedly in a program under a single name. When the value changes, only the constant definition is updated; all usage points are automatically updated. This eases maintenance and reduces errors.

Example: Suppose a game has static final int MAX_LIVES = 3;. If this constant is used in ten places, changing the maximum lives to 5 requires updating only the single definition. Without a constant, you would have written 3 in ten places and would need to find and update each one for a change. Constants also improve code readability; MAX_LIVES is more meaningful than 3.

Practice Add constants to Settings

Define a class Settings. Add a static final int MAX_USERS = 100 constant. Add a static final String APP_NAME = "Library" constant. In main print both constants' values on separate lines.

Starter code

Main.java
// Define the Settings class
// Add two constants
// Print in main

Sample solution

Main.java
class Settings {
    static final int MAX_USERS = 100;
    static final String APP_NAME = "Library";
    public static void main(String[] args) {
        System.out.println(Settings.MAX_USERS);
        System.out.println(Settings.APP_NAME);
    }
}

Expected output

100
Library

Questions and answers

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

1 What does final provide in: static final int MAX = 10;?

  • The value is accessible everywhere
  • The value cannot be changed Correct answer
  • The value becomes static
  • The value is deleted

Explanation: final ensures the value cannot be changed.

2 Complete the constant definition

Question 
class Settings {
    ____ int MAX_USERS = 100;
}
Answer 
class Settings {
    static final int MAX_USERS = 100;
}

Explanation: static final defines a constant.

3 Match the constant parts

Term Meaning
static Class level
final Immutability
MAX_USERS Constant name
100 Value

All lessons in Intermediate

1 Classes

  1. class
  2. Attributes
  3. Methods
  4. new
  5. toString
  6. Summary - Classes

2 Constructor

  1. Constructor basics
  2. Parameterized constructor
  3. Constructor overloading
  4. this()
  5. Default constructor
  6. Summary - Constructor

3 Inheritance

  1. extends
  2. super
  3. Method overriding
  4. Object class
  5. final class and method
  6. Summary - Inheritance

4 Project: Library

  1. Class design
  2. Book model
  3. Member management
  4. Borrow flow
  5. Putting it together

5 Encapsulation

  1. private fields
  2. Getter
  3. Setter
  4. Package-private
  5. Record
  6. Summary - Encapsulation

6 Static

  1. static fields
  2. static methods
  3. static block
  4. Class variables
  5. instanceof
  6. Summary - Static

7 Constants

  1. static final
  2. Uppercase convention
  3. Constants with enum
  4. Interface constants
  5. Math constants
  6. Summary - Constants

8 Project: Quiz app

  1. Quiz model
  2. Adding questions
  3. Running the quiz
  4. Score calculation
  5. Putting it together

9 Interface

  1. interface
  2. implements
  3. default methods
  4. static methods
  5. Multiple interfaces
  6. Summary - Interface

10 Abstract class

  1. abstract class
  2. abstract methods
  3. Abstract and concrete
  4. Abstract vs interface
  5. Sealed class
  6. Summary - Abstract class

11 Polymorphism

  1. Polymorphism basics
  2. Dynamic binding
  3. Override rules
  4. Abstract reference
  5. Pattern matching
  6. Summary - Polymorphism

12 Project: Blog app

  1. Model design
  2. Blog class
  3. Adding comments
  4. Search and filter
  5. Putting it together

13 File I/O

  1. File class
  2. FileReader and FileWriter
  3. BufferedReader
  4. PrintWriter
  5. try-with-resources
  6. Summary - File I/O

14 Serialization

  1. Jackson ObjectMapper
  2. readValue
  3. writeValueAsString
  4. JsonProperty
  5. List and Map serialization
  6. Summary - Serialization

15 Generics

  1. Generic class
  2. Generic method
  3. Bounded type
  4. Wildcard
  5. Type erasure
  6. Summary - Generics

16 Generic collections

  1. List<E>
  2. Map<K,V>
  3. Set<E>
  4. Queue and Deque
  5. Collections class
  6. Summary - Generic collections

17 Iterator

  1. Iterator
  2. remove
  3. ListIterator
  4. Iterable
  5. Spliterator
  6. Summary - Iterator

18 Lambda expressions

  1. Lambda basics
  2. Parameterized lambda
  3. Method reference
  4. forEach with lambda
  5. Comparator with lambda
  6. Summary - Lambda expressions

19 Stream API basics

  1. stream()
  2. filter
  3. map
  4. forEach and count
  5. collect toList
  6. Summary - Stream API basics

20 Intermediate final

  1. Project design
  2. OOP model
  3. Stream layer
  4. File I/O
  5. Putting it together