instanceof can be used here instead of isAssignableFrom

The right side is known at compile time.
And it's even a tiny tiny tiny bit faster
http://stackoverflow.com/questions/496928/what-is-the-difference-between-instanceof-and-class-isassignablefrom

Author: ralscha

bson/src/main/org/bson/codecs/DocumentCodec.java

@@ -166,9 +166,9 @@ private boolean skipField(final EncoderContext encoderContext, final String key)
     private void writeValue(final BsonWriter writer, final EncoderContext encoderContext, final Object value) {
         if (value == null) {
             writer.writeNull();
-        } else if (Iterable.class.isAssignableFrom(value.getClass())) {
+        } else if (value instanceof Iterable) {
             writeIterable(writer, (Iterable<Object>) value, encoderContext.getChildContext());
-        } else if (Map.class.isAssignableFrom(value.getClass())) {
+        } else if (value instanceof Map) {
             writeMap(writer, (Map<String, Object>) value, encoderContext.getChildContext());
         } else {
             Codec codec = registry.get(value.getClass());