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Asked: 2026-06-11T11:17:55+00:00

I have a class (EntireFile) that extends the LinkedHashMap. I try to cast: EntireFile

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I have a class (EntireFile) that extends the LinkedHashMap. I try to cast:

EntireFile old = (EntireFile) functionReturningLinkedHashMap();

It throws exception with message: “java.util.LinkedHashMap cannot be cast to com.gmail.maximsmol.YAML.GroupMap”.

public class EntireFile extends LinkedHashMap<String, GroupMap>

public class GroupMap extends LinkedHashMap<String, CategoryMap>

public class CategoryMap extends LinkedHashMap<String, LinkedHashMap<String, Integer>>

Please help me to solve the error!

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1 Answer

  1. Editorial Team

    The problem is that the reference returned simply isn’t a reference to an instance of EntireFile. If functionReturningLinkedHashMap just returns a LinkedHashMap, it can’t be cast to an EntireFile, because it isn’t one – how would it get any extra information about it?

    (Judging by your exception, you’re actually talking about GroupMap rather than EntireFile, but the same thing applies.)

    There’s nothing special about LinkedHashMap here – the same is always true in Java:

    Object foo = new Object();
String bar = (String) foo; // Bang! Exception
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