Where should enumerations (Enum) be used in Java?

Enums in Java should be used in cases where there is a fixed set of named constants. Typical usage scenarios:

• Representation of a fixed set of states or types. For example, days of the week, seasons, order statuses.
• Implementation of the Singleton pattern (although not the only way).
• Definition of a set of flags or options.
• Creating a limited set of discrete values that can be used in switch expressions.
• Replacing magic strings and numbers with named constants, improving code readability and safety.
• Grouping related constants and providing them with associated behaviors (methods).

Example of usage for order statuses:

public enum OrderStatus {
    NEW,
    PROCESSING,
    SHIPPED,
    DELIVERED,
    CANCELLED;

    // Can contain methods specific to the status
    public boolean isFinal() {
        return this == DELIVERED || this == CANCELLED;
    }
}