Java set witth enum values

Question

I have a java enum as

public enum Month {
        JANUARY("01. January")
        ,FEBRUARY("02. February")
        , MARCH("03. March")
        , APRIL("04. April")
        , MAY("05. May")
        , JUNE("06. June")
        , JULY("07. July")
        , AUGUST("08. August")
        , SEPTEMBER("09. September")
        , OCTOBER("10. October")
        , NOVEMBER("11. November")
        , DECEMBER("12. December");

        private final String displayName;

        Month(final String display)
        {
            this.displayName = display;
        }

        @Override public String toString()
        {
            return this.displayName;
        }

    };

Also I have a DTO Object which is

public class SampleDTO {

    private int variable1;

    private Set<String> monthName;

public int getVariable1() {
        return variable1;
    }

    public void setVariable1(int variable1) {
        this.variable1 = variable1;
    }

    public Set<String> getMonthName() {
        return monthName;
    }

    public void setMonthName(Set<String> monthName) {
        this.monthName = monthName;
    }

}

Last I have a method with input parameter as SampleDTO, Is there a way I can force that when a string is added to the monthName , it always comes from the valid values of the enum. for example adding "dfkjahdkjfadf" to the set should not be permitted

Answer 1

Change Set<String> to Set<Month> so that it can only contain Month enum instances. Making sure it is a legal month seems to be part of your contract, so you have to enforce it inside SampleDTO .

Answer 2

You might used Set<Month> instead of Set<String> , for example:

public class SampleDTO {
.    ...
     private Set<Month> month;
     ...
}