Java 列舉(Enum)範例
public enum WeekDay {
SUN("Sunday","星期日"),
MON("Monday","星期一"),
TUE("Tuesday","星期二"),
WED("Wednesday","星期三"),
THU("Thursday","星期四"),
FRI("Friday","星期五"),
SAT("Saturday","星期六");
WeekDay(String day, String chinese){
this.day = day;
this.chinese = chinese;
}
private final String day;
private final String chinese;
public static WeekDay getWeek(int i){
switch(i){
case 0: return SUN;
case 1: return MON;
case 2: return TUE;
case 3: return WED;
case 4: return THU;
case 5: return FRI;
case 6: return SAT;
default: return null;
}
}
public String getDay(){
return this.day;
}
public String getChinese(){
return this.chinese;
}
}
測試
public class Main {
public static void main(String[] args) {
WeekDay weekDay = WeekDay.getWeek(0);
System.out.println(weekDay.getDay());
System.out.println(weekDay.getChinese());
}
}
執行後印出如下
Sunday
星期日
原本取得WeekDay
的靜態方法getWeek()
中,是透過switch case
依傳入的參數來選擇對應的WeekDay
,下面範例進一步把switch case
消除。
public enum WeekDay {
SUN("Sunday","星期日", 0),
MON("Monday","星期一", 1),
TUE("Tuesday","星期二", 2),
WED("Wednesday","星期三", 3),
THU("Thursday","星期四", 4),
FRI("Friday","星期五", 5),
SAT("Saturday","星期六", 6);
WeekDay(String day, String chinese, int code){
this.day = day;
this.chinese = chinese;
this.code = code;
}
private final String day;
private final String chinese;
private int code;
public static WeekDay getWeek(int i){
for(WeekDay weekDay : values()){
if(weekDay.getCode() == i) {
return weekDay;
}
}
return null;
}
public String getDay(){
return this.day;
}
public String getChinese() {
return this.chinese;
}
public int getCode() {
return this.code;
}
}
在上面的WeekDay
新增了一個屬性code
及其getter,然後使用Enum本身的values()
方法可取得裝有列舉(星期一到星期日)的陣列,這樣便可以利用for迴圈與傳入的參數比對,數字相同則回傳該筆列舉。
注意Enum的values()
方法是由compiler提供,所以沒有Java Doc文件。values()
是靜態方法,呼叫後會回傳列舉中全部的值所組成的陣列,例如WeedDay.values()
的內容是
[SUN, MON, TUE, WED, THU, FRI, SAT]
如果文章有幫助還幫忙點個Google廣告,感恩。
2 則留言:
請問裡面的 switch case 是不是要加上 break 呢?
@Jimmy 不用喔,因為直接return了,不會往下走。
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