Java create instance of a generic type

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Create instance of generic type in Java?

In C# I can use the class Activator or default(T) but how can i do that in Java? I have a custom class like

public class Foo<T extends FooBase> ...

Now i want to create a instance of T(it has a public default ctor). I am new in java and I have no idea how I could create a instance of that "type". I've tried something like this:

T.class.newInstance();

but T has no .class? So what can I do?

what's wrong with calling the constructor like `new Foo()` (where `class Bar extends FooBase`) ? — Nevik Rehnel, Jan 03 '13 at 14:49
http://stackoverflow.com/a/12407106/1193090 answers your question nicely! — Reigo, Jan 03 '13 at 14:52
Looking at your question again, i think you might have a wrong concept of how generics work in java. you should read up on it, e.g. the answer and tutorial linked by Reigo above — Nevik Rehnel, Jan 03 '13 at 14:53
No, you can't: http://stackoverflow.com/questions/6101568/java-how-to-set-a-default-for-t-in-someclasst — Andrea Ligios, Jan 03 '13 at 14:57

Gangnus · Answer 1 · 2013-01-03T22:11:05.777

-1

You can use only existing constructor

public class Foo<T extends FooBase>{
    T base= (T) new FooBase();
}

edited Jan 03 '13 at 22:11

answered Jan 03 '13 at 14:54

Gangnus

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@jlordo If you have not a constructor FooBase(){}, then of course. – Gangnus Jan 03 '13 at 20:45
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no, you are missing the `new` keyword. – jlordo Jan 03 '13 at 20:46
Of course, foolish me. I see what must be there, not what is there. – Gangnus Jan 03 '13 at 20:48
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Now the obvious syntax error is gone. But it still won't compile. The compiler will tell you `Type mismatch: cannot convert from FooBase to T`. Just try it with an easy example. – jlordo Jan 03 '13 at 20:50
@jlordo yes, now I see, it needs (T), too. Thank you. Sorry. I checked it on IDE only now. – Gangnus Jan 03 '13 at 22:11

score -4 · Answer 2 · answered Jan 03 '13 at 14:50

-4

Class your_class = new Class() ;

answered Jan 03 '13 at 14:50

pidel

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Fails to include argument for the generic type – Nevik Rehnel Jan 03 '13 at 14:51

Java create instance of a generic type

2 Answers2