Simple Question: new() from Generic

Question

I have a simple Class:
public class Test<T>
  public void test()
    T obj = new T(); //error
}I get the error:
found : type parameter T
required: class
Suppose this isn't possible in java?
Thanks!

Answer 1

Not sure, if this is the real reason, but it sounds
logical to me: how would you guarantee a type T to
have the desired constructor and it being public? One
not even has to use Foo but could take any interface
or abstract class as example for T.
Java does not have an entity to describe contracts
for classes, so it's not possible.Why punish the other vast number of cases where the constructor is accessible then? Wouldn't it be a good idea to catch this at the point of erroneous usage.
I understand that Java is more restrictive in terms of what can be done with the type parameter, but since 'has a public no-arg constructor' is not a constraint that can be expressed in the language, it seems reasonable to allow access to it in the definition of the generic type.
I came across a similar discussion about erroring at point of usage:
class X<T, U extends Cloneable&T> { .... }The above is legal only if T is an interface. Should this not be allowed at the point of declaration of the generic type X or where a parameterized type X is being used with invalid type parameter? This has already been filed and accepted as a bug, though not fixed. http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4899305
At any rate, the error message is very unintuitive. What would be the good error message?
T may not have an accessible constructor?