Java enum

개요

열거형상수

• 예제 그냥 상수로 1주일을 표현했을때

public class EnumExample1 {

    private final static int MONDAY = 1;
    private final static int TUESDAY = 2;
    private final static int WEDNESDAY = 3;
    private final static int THURSDAY = 4;
    private final static int FRIDAY = 5;
    private final static int SATURDAY = 6;
    private final static int SUNDAY = 7;

    public static void main(String[] args) {        

        int day = MONDAY;

        switch (day) {
        case MONDAY:
            System.out.println("월요일 입니다.");
            break;
        case TUESDAY:
            System.out.println("화요일 입니다.");
            break;
        case WEDNESDAY:
            System.out.println("수요일 입니다.");
            break;
        }
    }
}

• interface를 이용한 방법

public class EnumExample2 {


interface DAY1{  
    int MONDAY = 1;
    int TUESDAY = 2;
    int WEDNESDAY = 3;
    int THURSDAY = 4;
    int FRIDAY = 5;
    int SATURDAY = 6;
    int SUNDAY = 7;
}

interface MONTH1{  
    int JANUARY = 1;
    int FEBRUARY = 2;
    int MARCH = 3;
    int APRIL = 4;
    int MAY =5;
    int JUNE = 6;
    int JULY = 7;
    int AUGUST = 8;
    int SEPTEMBER = 9;
    int OCTOBER = 10;
    int NOVEMBER = 11;
    int DECEMBER = 12;
}


    public static void main(String[] args) {

        if(DAY1.MONDAY == MONTH1.JANUARY){  // 이부분은 설계상 일치하면 안되는 부분이다. 논리적 오류
            System.out.println("두 상수는 같습니다.");
        }       

        int day = DAY1.MONDAY;

        switch (day) {
        case DAY1.MONDAY:
            System.out.println("월요일 입니다.");
            break;
        case DAY1.TUESDAY:
            System.out.println("화요일 입니다.");
            break;
        case DAY1.WEDNESDAY:
            System.out.println("수요일 입니다.");
            break;
        }
    }
}

• enum을 사용하여 다시 표현

public class EnumExample3 {

enum Day2{  
    MONDAY,TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY;
}

enum Month2{  
    JANUARY, FEBRUARY, MARCH, APRIL, MAY, JUNE, JULY, 
    AUGUST, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER;
}


    public static void main(String[] args) {        

        Day2 day = Day2.MONDAY;

        switch (day) {
        case MONDAY:
            System.out.println("월요일입니다.");
            break;
        case TUESDAY:
            System.out.println("화요일입니다.");
            break;
        case WEDNESDAY:
            System.out.println("수요일입니다.");
            break;
        }
    }
}