In what cases can the final modifier be used in Java?

The final modifier in Java can be applied to:

• Variables:
  • If the variable is of a primitive type, its value cannot be changed after initialization.
  • If the variable is of a reference type, the reference cannot be changed after initialization (the object cannot be reassigned), but the contents of the object can be modified.
• Methods:
  • A method declared with the final modifier cannot be overridden in subclasses.
• Classes:
  • A class declared with the final modifier cannot have subclasses (cannot be inherited).

Examples of usage:

// final primitive variable
final int MAX_VALUE = 100;

// final reference variable
final List<String> names = new ArrayList<>();
names.add("Alice"); // Modifying the object's contents is allowed
// names = new LinkedList<>(); // Reassignment is not allowed

// final method
public final void processData() {
    // method logic
}

// final class
public final class ImmutableClass {
    // fields and methods
}

Using final helps to:

• Ensure data immutability.
• Prevent unwanted method overriding or class inheritance.
• Allow the compiler to perform optimizations.
• Improve code readability by explicitly indicating restrictions.