How to write a method that accepts any collection of classes that extend Throwable?

Question

I want to pass a set of classes that extend a method Throwableto a method. However, my attempt was not compiled in Netbeans with jdk1.6.0_39:

package com.memex.sessionmanager;

import java.util.Collection;
import java.util.Collections;

public class GenericsDemo
{
    public void foo(Collection<Class<? extends Throwable>> c)
    {
    }

    public void bar()
    {
        foo(Collections.singleton(RuntimeException.class));
    }
}

The compiler says foo(java.util.Collection<java.lang.Class<? extends java.lang.Throwable>>) in com.memex.sessionmanager.GenericsDemo cannot be applied to (java.util.Set<java.lang.Class<java.lang.RuntimeException>>).

I can compile it by changing the call code to:

foo(Collections.<Class<? extends Throwable>>singleton(RuntimeException.class));

but I would rather not force clients to write this dumb generic type. Is it possible to write a method that takes any set of classes, a subtype Throwable?

EDIT:

Someone fixed the above example using the method signature:

public <T extends Throwable> void foo(Collection<Class<T>> c) {}

But now I have problems with the parameter. In particular, I want to assign it to a field, for example:

package com.memex.sessionmanager;

import java.util.Collection;
import java.util.Collections;

public class GenericsDemo
{

    private Collection<Class<? extends Throwable>> throwables;

    public <T extends Throwable> void foo(Collection<Class<T>> c)
    {
        throwables = c;
    }

    public void bar()
    {
        foo(Collections.singleton(RuntimeException.class));
    }
}

But the compiler says:

incompatible types
found   : java.util.Collection<java.lang.Class<T>>
required: java.util.Set<java.lang.Class<? extends java.lang.Throwable>>

Answer 1

Java 7:

import java.util.Collection;
import java.util.Collections;

public class Generics {
  public void foo(Collection<? extends Class<? extends Throwable>> c) { 
  }

  {
    foo(Collections.singleton(RuntimeException.class));
  }
}

Answer 2

public <T extends Throwable> void foo(Collection<Class<T>> c) {}