diff -r 1c999569643b -r acf2c31e22d4 samples/instanceofclass/src-api2.0/api/InstanceProvider.java
--- a/samples/instanceofclass/src-api2.0/api/InstanceProvider.java	Sat Jun 14 10:04:51 2008 +0200
+++ b/samples/instanceofclass/src-api2.0/api/InstanceProvider.java	Sat Jun 14 10:04:53 2008 +0200
@@ -2,24 +2,50 @@
 package api;
 
 // BEGIN: instanceof.class.InstanceProvider2
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.concurrent.Callable;
+
 public final class InstanceProvider {
-    private final Object instance;
+    private final Callable<Object> instance;
+    private final Set<String> types;
 
-    public InstanceProvider(Object instance) {
+    public InstanceProvider(Callable<Object> instance) {
         this.instance = instance;
+        this.types = null;
+    }
+    /** Specifies not only a factory for creating objects, but
+     * also additional information about them.
+     * @param instance the factory to create the object
+     * @param type the class that the create object will be instance of
+     * @since 2.0 
+     */
+    public InstanceProvider(Callable<Object> instance, String... types) {
+        this.instance = instance;
+        this.types = new HashSet<String>();
+        this.types.addAll(Arrays.asList(types));
     }
     
-    public Class<?> instanceClass() {
-        return instance.getClass();
+    public Class<?> instanceClass() throws Exception {
+        return instance.call().getClass();
     }
-    public Object instanceCreate() {
-        return instance;
+    public Object instanceCreate() throws Exception {
+        return instance.call();
     }
     
-    /** @since 2.0 */
-    public boolean isInstanceOf(Class<?> c) {
-        if (Helper.knownHowToDoItBetter()) {
-            return Helper.computeTheResultOfIsInstanceOfInSomeBetterWay(c);
+    /** Allows to find out if the InstanceProvider creates object of given
+     * type. This check can be done without loading the actual object or
+     * its implementation class into memory.
+     * 
+     * @param c class to test 
+     * @return if the instances produced by this provider is instance of c
+     * @since 2.0 
+     */
+    public boolean isInstanceOf(Class<?> c) throws Exception {
+        if (types != null) {
+            return types.contains(c.getName());
         } else {
             // fallback
             return c.isAssignableFrom(instanceClass());
@@ -29,12 +55,3 @@
     
 }
 // END: instanceof.class.InstanceProvider2
-
-class Helper {
-    static boolean computeTheResultOfIsInstanceOfInSomeBetterWay(Class<?> c) {
-        return false;
-    }
-    static boolean knownHowToDoItBetter() {
-        return false;
-    }
-}
\ No newline at end of file