覆盖 Java 枚举中的 valueof() 和 toString()
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Override valueof() and toString() in Java enum
提问by WildBamaBoy
The values in my enumare words that need to have spaces in them, but enums can't have spaces in their values so it's all bunched up. I want to override toString()to add these spaces where I tell it to.
myenum中的值是需要在其中包含空格的单词，但是枚举的值中不能包含空格，因此它们都被捆绑在一起。我想覆盖toString()以在我告诉它的地方添加这些空格。
I also want the enum to provide the correct enum when I use valueOf()on the same string that I added the spaces to.
当我valueOf()在添加空格的同一个字符串上使用时，我还希望枚举提供正确的枚举。
For example:
例如：
public enum RandomEnum
{
StartHere,
StopHere
}
Call toString()on RandomEnumwhose value is StartHerereturns string "Start Here". Call valueof()on that same string ("Start Here") returns enum value StartHere.
电话toString()上的RandomEnum，其值是StartHere返回字符串"Start Here"。调用valueof()同一个字符串 ( "Start Here") 返回枚举值StartHere。
How can I do this?
我怎样才能做到这一点？
采纳答案by Jugal Shah
You can try out this code. Since you cannot override valueOfmethod you have to define a custom method (getEnumin the sample code below) which returns the value that you need and change your client to use this method instead.
你可以试试这个代码。由于您无法覆盖valueOf方法，因此您必须定义一个自定义方法（getEnum在下面的示例代码中），该方法返回您需要的值并更改您的客户端以使用此方法。
public enum RandomEnum {
StartHere("Start Here"),
StopHere("Stop Here");
private String value;
RandomEnum(String value) {
this.value = value;
}
public String getValue() {
return value;
}
@Override
public String toString() {
return this.getValue();
}
public static RandomEnum getEnum(String value) {
for(RandomEnum v : values())
if(v.getValue().equalsIgnoreCase(value)) return v;
throw new IllegalArgumentException();
}
}
回答by Java42
I don't think your going to get valueOf("Start Here") to work. But as far as spaces...try the following...
我认为您不会让 valueOf("Start Here") 起作用。但就空间而言...请尝试以下...
static private enum RandomEnum {
R("Start There"),
G("Start Here");
String value;
RandomEnum(String s) {
value = s;
}
}
System.out.println(RandomEnum.G.value);
System.out.println(RandomEnum.valueOf("G").value);
Start Here
Start Here
回答by exception
The following is a nice generic alternative to valueOf()
以下是 valueOf() 的一个很好的通用替代方案
public static RandomEnum getEnum(String value) {
for (RandomEnum re : RandomEnum.values()) {
if (re.description.compareTo(value) == 0) {
return re;
}
}
throw new IllegalArgumentException("Invalid RandomEnum value: " + value);
}
回答by pedorro
You can use a static Map in your enum that maps Strings to enum constants. Use it in a 'getEnum' static method. This skips the need to iterate through the enums each time you want to get one from its String value.
您可以在枚举中使用静态 Map 将字符串映射到枚举常量。在“getEnum”静态方法中使用它。这跳过了每次您想从其 String 值中获取枚举时迭代枚举的需要。
public enum RandomEnum {
StartHere("Start Here"),
StopHere("Stop Here");
private final String strVal;
private RandomEnum(String strVal) {
this.strVal = strVal;
}
public static RandomEnum getEnum(String strVal) {
if(!strValMap.containsKey(strVal)) {
throw new IllegalArgumentException("Unknown String Value: " + strVal);
}
return strValMap.get(strVal);
}
private static final Map<String, RandomEnum> strValMap;
static {
final Map<String, RandomEnum> tmpMap = Maps.newHashMap();
for(final RandomEnum en : RandomEnum.values()) {
tmpMap.put(en.strVal, en);
}
strValMap = ImmutableMap.copyOf(tmpMap);
}
@Override
public String toString() {
return strVal;
}
}
Just make sure the static initialization of the map occurs below the declaration of the enum constants.
只需确保映射的静态初始化发生在枚举常量的声明下方。
BTW - that 'ImmutableMap' type is from the Google guava API, and I definitely recommend it in cases like this.
顺便说一句 - 'ImmutableMap' 类型来自 Google guava API，在这种情况下我绝对推荐它。
EDIT - Per the comments:
编辑 - 根据评论：
- This solution assumes that each assigned string value is unique and non-null. Given that the creator of the enum can control this, and that the string corresponds to the unique & non-null enum value, this seems like a safe restriction.
- I added the 'toSTring()' method as asked for in the question
- 此解决方案假定每个分配的字符串值都是唯一且非空的。鉴于枚举的创建者可以控制这一点，并且字符串对应于唯一且非空的枚举值，这似乎是一个安全的限制。
- 我添加了问题中要求的“toSTring()”方法
回答by Bat
Try this, but i don't sure that will work every where :)
试试这个，但我不确定它是否适用于所有地方:)
public enum MyEnum {
A("Start There"),
B("Start Here");
MyEnum(String name) {
try {
Field fieldName = getClass().getSuperclass().getDeclaredField("name");
fieldName.setAccessible(true);
fieldName.set(this, name);
fieldName.setAccessible(false);
} catch (Exception e) {}
}
}
回答by corlaez
How about a Java 8 implementation? (null can be replaced by your default Enum)
Java 8 实现怎么样？（null 可以替换为您的默认 Enum）
public static RandomEnum getEnum(String value) {
List<RandomEnum> list = Arrays.asList(RandomEnum.values());
return list.stream().filter(m -> m.value.equals(value)).findAny().orElse(null);
}
Or you could use:
或者你可以使用：
...findAny().orElseThrow(NotFoundException::new);
回答by Andrey Lebedenko
You still have an option to implement in your enum this:
您仍然可以选择在您的枚举中实现：
public static <T extends Enum<T>> T valueOf(Class<T> enumType, String name){...}
