fixes a bug reported in #228

src/main/javassist/util/proxy/ProxyFactory.java

@@ -622,7 +622,9 @@ public class ProxyFactory {
      * {@code java.lang.invoke.MethodHandles.Lookup}.
      */
     private Class<?> getClassInTheSamePackage() {
-        if (superClass != null && superClass != OBJECT_TYPE)
+        if (basename.startsWith("javassist.util.proxy."))       // maybe the super class is java.*
+            return this.getClass();
+        else if (superClass != null && superClass != OBJECT_TYPE)
             return superClass;
         else if (interfaces != null && interfaces.length > 0)
             return interfaces[0];

src/test/javassist/proxyfactory/ProxyFactoryTest.java

@@ -128,4 +128,16 @@ public class ProxyFactoryTest extends TestCase {
     public static class TestDefaultC2 extends TestDefaultC {
         public int baz() { return super.foo(); }
     }
+
+    public void testJava11() throws Exception {
+        ProxyFactory factory = new ProxyFactory();
+        factory.setSuperclass(java.util.HashMap.class);
+        java.util.HashMap e = (java.util.HashMap)factory.create(null, null, new MethodHandler() {
+            @Override
+            public Object invoke(Object self, Method thisMethod,
+                    Method proceed, Object[] args) throws Throwable {
+                return proceed.invoke(self, args);
+            }
+        });
+    }
 }