Explain the concept of the Int Enum pattern in programming

The Int Enum pattern in programming is a way to represent enumerations (enum) using integer values. In Java, for example, you can create an enum where each element corresponds to a specific integer value. This is useful when you need to map enum values to numbers, for instance, for database storage or interaction with external systems.

Example in Java:

public enum Status {
    NEW(0),
    IN_PROGRESS(1),
    DONE(2);

    private final int code;

    Status(int code) {
        this.code = code;
    }

    public int getCode() {
        return code;
    }

    public static Status fromCode(int code) {
        for (Status status : Status.values()) {
            if (status.code == code) {
                return status;
            }
        }
        throw new IllegalArgumentException("Unknown code: " + code);
    }
}

This approach allows for convenient working with enums while having a numeric representation for integration or optimization.