Java - enum 類別

1.何謂enum?

enum定義的xxxx實際上是個類別

2.為何要有enum?
在interface中，可以定義常數。例如：

public interface Action {
    public static final int STOP = 0;
    public static final int RIGHT = 1;
    public static final int LEFT = 2;
    public static final int UP = 3;
    public static final int DOWN = 4;
} 

但後面在取用時只能透過Action.STOP這種方式取，但其實不易讀 之後發展出enum，使用起來更為方便

3.實際應用

例子1

public class  test {

    //設定建構子
    public enum Level {
        DOWNLOAD_QUANTITY(0, "AA"),
        DOWNLOAD_CONTENT(1, "BB"),
        KEYWORD_LENGTH(2, "CC"),
        STANDARD_PLATFORM_LOGIN(3, "登入"),
        EDUCATION_VIEW(4, "DD");

        private int mode;
        private String Name;

        private Level(int mode, String Name) {
            this.mode = mode;
            this.Name = Name;
        }
    }

    //執行程式(提示：Level.STANDARD_PLATFORM_LOGIN 等於把STANDARD_PLATFORM_LOGIN常數的值塞入建構子內)
    public static void main(String[] args) {
        int n = Level.STANDARD_PLATFORM_LOGIN.mode;
        String s = Level.STANDARD_PLATFORM_LOGIN.Name;
        System.out.println(n); //3
        System.out.println(s); //登入
    }

}

例子2