CODEWITHSUNDEEP
javaenums
Squid_Vicious
Squid_Vicious

Reputation: 147

Java Enums confusion

I am trying to get my head around enums, some lines of code have me slightly confused. This is taken straight from the oracle docs site but having a little trouble understanding a few lines of code : 

public class EnumTest {
    public enum Day {
        SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
        THURSDAY, FRIDAY, SATURDAY 
   }
    Day day;

    public EnumTest(Day day) {
    this.day = day;
    }

The first 5 lines (class EnumTest) is quite ok, self explanatory really. What I dont understand are the last 5 lines of the above code, confusing. Could someone please explain their meaning within the context of the complete code below? Enumtest(Day day) is obviously a method , its the "this.day = day" and the preceding "Day day" I dont get .....

Complete code :

public class EnumTest {
    public enum Day {
        SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
        THURSDAY, FRIDAY, SATURDAY 
    }
    Day day;

    public EnumTest(Day day) {
    this.day = day;
    }

    public void tellItLikeItIs() {
        switch (day) {
            case MONDAY:
                System.out.println("Mondays are bad.");
                break;

            case FRIDAY:
                System.out.println("Fridays are better.");
                break;

            case SATURDAY: case SUNDAY:
            System.out.println("Weekends are best.");
            break;

        default:
            System.out.println("Midweek days are so-so.");
            break;
        }
    }

    public static void main(String[] args) {
        EnumTest firstDay = new EnumTest(Day.MONDAY);
        firstDay.tellItLikeItIs();
        EnumTest thirdDay = new EnumTest(Day.WEDNESDAY);
        thirdDay.tellItLikeItIs();
        EnumTest fifthDay = new EnumTest(Day.FRIDAY);
        fifthDay.tellItLikeItIs();
        EnumTest sixthDay = new EnumTest(Day.SATURDAY);
        sixthDay.tellItLikeItIs();
        EnumTest seventhDay = new EnumTest(Day.SUNDAY);
        seventhDay.tellItLikeItIs();
    }
}

Upvotes: 2

Views: 239

Answers (1)

jhobbie
jhobbie

Reputation: 1016

Actually, it's not really a method the way you think it is. If you notice, there's a new class called EnumTest, so what you're actually seeing is the constructor. And then the line below it, this.day = day sets the day for any instance of an object of class EnumTest using the input into the constructor. Sample code that could run in the main method would be:

EnumTest fri = new EnumTest(Day.FRIDAY);

Since there is no return type (i.e. void or int etc.) you can tell it's a constructor. Another clue is that it has the same name is the class that holds it.

Upvotes: 6

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