CODEWITHSUNDEEP
javagenericsgeneric-list
Kooki
Kooki

Reputation: 1157

Return generic list

I want to load a generic list. Therefore I want to use a function like :

public static <T> List<T> load()
{
    FileInputStream fileStream = null;
    List<T> toReturn = new ArrayList<T>();
    String fileExtension = toReturn.getClass().getComponentType().getSimpleName();
    ...
}

if you can see I want to get the Type ("T"), to search for files with these extensions. But if I call :

StorageUtil.<MyClass>load();

I get an Exception instead of getting "MyClass" as fileExtension. What's wrong on my code?

Upvotes: 1

Views: 569

Answers (1)

Jon Skeet
Jon Skeet

Reputation: 1503459

The problem is that generics in Java don't work that way - you can't find the type of T at execution time due to type erasure. If you need the type at execution time, you can add a Class<T> parameter:

public static <T> List<T> load(Class<T> clazz) {
    ... use class.newInstance() to create a new instance, etc
}

See the Java Generics FAQ entry for Type Erasure for more information.

Upvotes: 8

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