[英]Trying to write a generic enum util class in groovy
We have multiple enum types that have some public static EnumType valueOfText(String text)
, for the purpose of mapping the contents of a data file cell to enum.我们有多个枚举类型,它们具有一些
public static EnumType valueOfText(String text)
,目的是将数据文件单元格的内容映射到枚举。
I'm trying to write a generic enum util that takes a comma-separated string and return multiple enum values.我正在尝试编写一个通用的枚举实用程序,它采用逗号分隔的字符串并返回多个枚举值。 For example, we have the following enum:
例如,我们有以下枚举:
public enum Frequency {
SEMI_ANNUAL("S"), MONTHLY("M"), QUARTERLY("Q"), ANNUAL("A")
public final String textValue;
public Frequency(String textValue) {
this.textValue = textValue;
}
public static Frequency valueOfText(String textValue) {
for (Frequency frequency : values()) {
if (frequency.textValue.equals(textValue))
return frequency;
}
return null;
}
}
and string "A,S"
which we want to convert to [Frequency.ANNUAL, Frequency.SEMI_ANNUAL]
.和我们想要转换为
[Frequency.ANNUAL, Frequency.SEMI_ANNUAL]
字符串"A,S"
。
I create some EnumUtils
like so:我像这样创建了一些
EnumUtils
:
import java.util.stream.Collectors
public final class EnumUtils {
public static final String LIST_SEPARATOR = ",";
public static <E extends Enum<E>> List<E> CreateFromText(String text) {
List<String> textList = text.split(this.LIST_SEPARATOR)
return textList.stream()
.map { txt ->
E.valueOfText(txt)
}
.collect(Collectors.toList())
}
}
We go to use it, like this:我们去使用它,像这样:
EnumUtils.CreateFromText<Frequency>(row[3])
and the IDE compain, immediately, about the <>
.和 IDE compain,立即,关于
<>
。
How can we specify enum type in this?我们如何在此指定枚举类型?
In Groovy you can do it if you pass the actual Class
instead of just using a type parameter.在 Groovy 中,如果传递实际的
Class
而不是仅使用类型参数,则可以执行此操作。
enum Frequency {
SEMI_ANNUAL("S"), MONTHLY("M"), QUARTERLY("Q"), ANNUAL("A")
final String textValue;
Frequency(String textValue) {
this.textValue = textValue;
}
static Frequency valueOfText(String textValue) {
return values().find { it.textValue == textValue }
}
}
final class EnumUtils {
static <E extends Enum<E>> List<E> createFromText(Class<E> clazz, String text) {
return text.split(",").collect { clazz.valueOfText(it) }
}
}
EnumUtils.createFromText(Frequency, "S,M")
The same idea won't work in Java, since clazz
won't have valueOfText
at compile time.同样的想法在 Java 中不起作用,因为
clazz
在编译时没有valueOfText
。
Perhaps the Util class doesn't save you much typing, though:不过,也许 Util 类不会为您节省太多输入:
"S,M".split(",").collect(Frequency.&valueOfText)
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