How to assign a value to each enum object, such as month number on a Month enum?

Question

I am new to Java so I don't really know much can you help me as simply as possible. This is my code; I got an error about the month(int) so that means it cannot import the library.

public enum Month {
    January(1), February(2), March(3), April(4),May(5),June(6), July(7), August(8), September(9), October(10),  November(11), December(12)
}

ERROR:Description Resource Path Location Type The constructor Month(int) is undefined Month.java /tb00594_comp1027_formative2/src/tb00594_comp1027_formative2 line 4 Java Problem

WARNING:Description Resource Path Location Type Build path specifies execution environment JavaSE-1.7. There are no JREs installed in the workspace that are strictly compatible with this environment. tb00594_comp1027_formative2 Build path JRE System Library Problem

So if you can help me as quickly as possible I would be greatefull.

Answer 1

Enum is basically declaration of final set of passible options (in your case months). But it is still Java Class ~ Object.

Your error literally says you are missing constructor for Java Class while you want to give every enumeration certain property. I guess you want to add month order in calendar. All you need to do is just declare property of class and enum constructor.

public enum Month {
    // Enum definition. Passing value to constructor. 
    JANUARY(1), FEBRUARY(2), MARCH(3), APRIL(4),MAY(5),JUNE(6), JULY(7), AUGUST(8), SEPTEMBER(9), OCTOBER(10),  NOVEMBER(11), DECEMBER(12);

    // Member field.
    private int monthOrder;

    // Constructor.
    public Month (int monthOrder) {
        this.monthOrder = monthOrder;
    }

    // Accessor.
    public int getMonthOrder() {
        return this.monthOrder;
    }
 }

See similar code run at Ideone.com.

Answer 2

You have to write constructor for enum. So you need to implement like this;

public enum Month {
    January(1), February(2), March(3), April(4), May(5), June(6), July(7), August(8), September(9), October(10), November(11), December(12);

    private int value;

    Month(int i) {
        this.value = i;
    }

}

As you can see the constructor ;

Month(int i) {
    this.value = i;
} 

which is giving the integer value of related month.And set to value field of enum which is keep the month's value.