在switch / case中使用enum [英] using enum in switch/case
问题描述
我有一个具有枚举属性的实体:
I have an entity that has an enum property:
// MyFile.java
public class MyFile {
private DownloadStatus downloadStatus;
// other properties, setters and getters
}
// DownloadStatus.java
public enum DownloadStatus {
NOT_DOWNLOADED(1),
DOWNLOAD_IN_PROGRESS(2),
DOWNLOADED(3);
private int value;
private DownloadStatus(int value) {
this.value = value;
}
public int getValue() {
return value;
}
}
我想将此实体保存在数据库中并检索它。问题是我将int值保存在数据库中,并获得int值!我不能使用如下所示的开关:
I want to save this entity in database and retrieve it. The problem is that I save the int value in database and I get int value! I can not use switch like below:
MyFile file = new MyFile();
int downloadStatus = ...
switch(downloadStatus) {
case NOT_DOWNLOADED:
file.setDownloadStatus(NOT_DOWNLOADED);
break;
// ...
}
我该怎么办?
推荐答案
您可以在枚举中提供静态方法:
You could provide a static method in your enum:
public static DownloadStatus getStatusFromInt(int status) {
//here return the appropriate enum constant
}
然后在您的主要代码中:
Then in your main code:
int downloadStatus = ...;
DowloadStatus status = DowloadStatus.getStatusFromInt(downloadStatus);
switch (status) {
case DowloadStatus.NOT_DOWNLOADED:
//etc.
}
这与序数方法的优势在于它仍然有效如果您的枚举更改为:
The advantage of this vs. the ordinal approach, is that it will still work if your enum changes to something like:
public enum DownloadStatus {
NOT_DOWNLOADED(1),
DOWNLOAD_IN_PROGRESS(2),
DOWNLOADED(4); /// Ooops, database changed, it is not 3 any more
}
请注意 getStatusFromInt
的初始实现可能会使用ordinal属性,但该实现细节现在包含在枚举类中。
Note that the initial implementation of the getStatusFromInt
might use the ordinal property, but that implementation detail is now enclosed in the enum class.
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