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POjava: reflection to obtain an Enum
primarykey
Id
4750965
data
AcceptedAnswerId
4751239
AnswerCount
2
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2011-01-20T18:25:50.760
FavoriteCount
0
LastActivityDate
2014-10-13T12:47:56.713
LastEditDate
2017-05-23T10:33:08.147
LastEditorUserId
-1
OwnerUserId
44330
ParentId
0
PostTypeId
1
Score
8
ViewCount
16659
LastEditorDisplayName
text
Body
This is similar but not quite the same as <a href="https://stackoverflow.com/questions/3735927/java-instantiating-an-enum-using-reflection">Java: instantiating an enum using reflection</a> I have a <code>Map<Enum<?>, FooHandler></code> that I want to use to map <code>Enum</code>s (I don't care which type or even if they are the same type, just as long as they are enum constants) to my <code>FooHandler</code> class. I would like to populate this map using a text file that I read. I can get it to work, but I have two warnings I would like to get around: <pre><code>static private <E extends Enum<E>> E getEnum(String enumFullName) { // see https://stackoverflow.com/questions/4545937/ String[] x = enumFullName.split("\\.(?=[^\\.]+$)"); if (x.length == 2) { String enumClassName = x[0]; String enumName = x[1]; try { Class<E> cl = (Class<E>)Class.forName(enumClassName); // #1 return Enum.valueOf(cl, enumName); } catch (ClassNotFoundException e) { e.printStackTrace(); } } return null; } public void someMethod(String enumName, String fooHandlerName) { FooHandler fooHandler = getFooHandler(fooHandlerName); Enum e = getEnum(enumName); // #2 map.put(e, fooHandler); } </code></pre> Warning #1: unchecked cast Warning #2: Enum is a raw type. I get #1 and could just put a warning I suppose, but I can't seem to beat warning #2; I've tried <code>Enum<?></code> and that just gives me an error about generic type capture bound mismatch. <hr> Alternative implementations that are worse: Before my <code><E extends Enum<E>></code> generic return value, I tried returning Enum and it didn't work; I got these warnings/errors: <pre><code>static private Enum<?> getEnum(String enumFullName) { ... Class<?> cl = (Class<?>)Class.forName(enumClassName); // 1 return Enum.valueOf(cl, enumName); // 2 } </code></pre> <ol> <li>warnings: <pre><code> - Type safety: Unchecked cast from Class<capture#3-of ?> to Class<Enum> - Enum is a raw type. References to generic type Enum<E> should be parameterized - Enum is a raw type. References to generic type Enum<E> should be parameterized - Unnecessary cast from Class<capture#3-of ?> to Class<?> </code></pre></li> <li>errors: <pre><code>- Type mismatch: cannot convert from capture#5-of ? to Enum<?> - Type safety: Unchecked invocation valueOf(Class<Enum>, String) of the generic method valueOf(Class<T>, String) of type Enum - Bound mismatch: The generic method valueOf(Class<T>, String) of type Enum<E> is not applicable for the arguments (Class<capture#5-of ?>, String). The inferred type capture#5-of ? is not a valid substitute for the bounded parameter <T extends Enum<T>> </code></pre></li> </ol> and this: <pre><code>static private Enum<?> getEnum(String enumFullName) { ... Class<Enum<?>> cl = (Class<Enum<?>>)Class.forName(enumClassName); // 1 return Enum.valueOf(cl, enumName); // 2 </code></pre> <ol> <li>warning: <code>Type safety: Unchecked cast from Class<capture#3-of ?> to Class<Enum<?>></code></li> <li>error: <code>Bound mismatch: The generic method valueOf(Class<T>, String) of type Enum<E> is not applicable for the arguments (Class<Enum<?>>, String). The inferred type Enum<?> is not a valid substitute for the bounded parameter <T extends Enum<T>></code></li> </ol>
Tags
<java><reflection><enums>
Title
java: reflection to obtain an Enum
singulars
PostAcceptedAnswerId
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
PostParentId
1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
UserLastEditorUserId
1. USCommunity
UserOwnerUserId
1. USJason S
plurals
PostLinksPostIdRelatedPostId
1. PL
 singulars
 LinkTypeLinkTypeId
 LTLinked
2. PL
 singulars
 LinkTypeLinkTypeId
 LTLinked
PostLinksRelatedPostIdPostId
1. PL
 singulars
 LinkTypeLinkTypeId
 LTLinked
2. PL
 singulars
 LinkTypeLinkTypeId
 LTLinked
PostsAcceptedAnswerId
1. This table or related slice is empty.
PostsParentIdCreationDate
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
2. PO
 singulars
 PostTypePostTypeId
 PTAnswer
VotesPostIdCreationDate
1. VO
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 PostPostId
 POjava: reflection to obtain an Enum
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTUpMod
2. VO
 singulars
 PostPostId
 POjava: reflection to obtain an Enum
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTUpMod
3. VO
 singulars
 PostPostId
 POjava: reflection to obtain an Enum
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTUpMod
CommentsPostId
1. This table or related slice is empty.

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