Enum

• https://www.mkyong.com/java/java-enum-example/

public enum UserStatus {
    PENDING,
    ACTIVE,
    INACTIVE,
    DELETED;
}

System.out.println(UserStatus.ACTIVE);      //ACTIVE

public enum WhoisRIR {
    ARIN("whois.arin.net"),
    RIPE("whois.ripe.net"),
    APNIC("whois.apnic.net"),
    AFRINIC("whois.afrinic.net"),
    LACNIC("whois.lacnic.net"),
    JPNIC("whois.nic.ad.jp"),
    KRNIC("whois.nic.or.kr"),
    CNNIC("ipwhois.cnnic.cn"),
    UNKNOWN("");

    private String url;

    WhoisRIR(String url) {
        this.url = url;
    }

    public String url() {
        return url;
    }
}

        System.out.println(WhoisRIR.ARIN.url());      //whois.arin.net

public enum Operation {
    PLUS,
    MINUS,
    TIMES,
    DIVIDE;

    double calculate(double x, double y) {
        switch (this) {
            case PLUS:
                return x + y;
            case MINUS:
                return x - y;
            case TIMES:
                return x * y;
            case DIVIDE:
                return x / y;
            default:
                throw new AssertionError("Unknown operations " + this);
        }
    }

}

        double result = Operation.PLUS.calculate(1, 2);
        System.out.println(result); //3.0

        for (UserStatus status : UserStatus.values()) {
            System.out.println(status);
        }

PENDING
ACTIVE
INACTIVE
DELETED

        WhoisRIR rir = WhoisRIR.APNIC;

        if(rir == WhoisRIR.APNIC) {
            System.out.println("This is APNIC : " + rir.url());
        }