java enum vs interface vs class constants

public enum EnumEx {

    MALE("male"),FEMALE("");
    private String value;

    EnumEx(String value){
        this.value = value;
    };

    public String value() {
        return value;
    }
}

public class TestEx {
    public static void main(String[] args) {
        System.out.println(EnumEx.MALE.value()); // custom method value()
        System.out.println(EnumEx.MALE.name()); // predefined method name()
    }
}

output:

male
MALE

=============================================

Can avoid using:

public interface Constants{

  String MALE = "male";

  .....

}

Enum by default is Singleton and it's threadsafe.