Java Generic Method - Cannot instantiate Class with generic parameter

Question

Following example is not the original code, I'm not looking for a workaround.

There is a Class For Generic Parsing/UnMarshalling like:

public class UnMarshaller<T extends AClass> {
...

This works fine, until I try to provide a Generic Method to access it.

public class UnMarshall{
...
// the T schema is every time a Subclass of AClass
public <T extends AClass> Queue<T> instantiateSomething(Input i, T schema) {
    UnMarshaller<schema> unmarshaller= new UnMarshaller<schema>(schema, i);
    return unmarshaller.getQueue();
}
...

UnMarshaller<schema> and new UnMarshaller<schema> are troubleing, but i doesn't get it. How can I instantiate this class?

rgettman · Accepted Answer · 2013-10-15 22:16:44Z

3

When using a generic type parameter, supply the class/type name, not the variable name:

UnMarshaller<T> unmarshaller = new UnMarshaller<T>(schema, i);

answered Oct 15, 2013 at 22:16

rgettman

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2 Comments

MemLeak Over a year ago

Its working. So the schema is useless? I'm able to do the method call like <SubClasOfA>instantiateSomething(new Input()); ?

rgettman Over a year ago

It doesn't look like schema is useless, depending on its purpose. You pass it to the UnMarshaller constructor. If the only purpose of it is to define T, then it's not necessary.

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