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Generics Question: Map and Map.Entry

Mr. C Lamont Gilbert
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Joined: Oct 05, 2001
Posts: 1170

I am using the Map class and calling the entrySet() method. Its defined


I tried to call it like so


I am using Java 1.5.0_22 and Eclipse 3.2.2. It won't let me type this. It insists on having

Set<? extends Map.Entry<? extends IProperty,? extends String>> properties = propHolder.getProperties().entrySet();

This does not make sense to me. Is this a compiler or Eclipse error? I haven't manually compiled Java in so long, I figured it be faster for me to ask than to try and manually invoke the java compiler. I know Eclipse uses its own internal compiler for identifying errors and debugging sessions. I can't figure out why this should not be allowed.
Andrey Kozhanov
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Joined: Mar 12, 2010
Posts: 79
Lets suppose we have two classes: Then our Map could contain Map.Entry<C1, String> and Map.Entry<C2, String>. My guess is that this is not the same Map.Entries, that's why you need to put Set<? extends Map.Entry>.
Mr. C Lamont Gilbert
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Joined: Oct 05, 2001
Posts: 1170

I don't think so. Map.Entry<C1,String> is not the same as Map.Entry<C2,String>. Besides, the Map.Entry is defined in the Map method, so there is no choice between the two.
 
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subject: Generics Question: Map and Map.Entry