In order to access private fields, you need to get them from the class’s declared fields and then make them accessible:
Field f = obj.getClass().getDeclaredField("stuffIWant"); //NoSuchFieldException f.setAccessible(true); Hashtable iWantThis = (Hashtable) f.get(obj); //IllegalAccessException
EDIT: as has been commented by aperkins, both accessing the field, setting it as accessible and retrieving the value can throw
Exceptions, although the only checked exceptions you need to be mindful of are commented above.
NoSuchFieldException would be thrown if you asked for a field by a name which did not correspond to a declared field.
obj.getClass().getDeclaredField("misspelled"); //will throw NoSuchFieldException
IllegalAccessException would be thrown if the field was not accessible (for example, if it is private and has not been made accessible via missing out the
RuntimeExceptions which may be thrown are either
SecurityExceptions (if the JVM’s
SecurityManager will not allow you to change a field’s accessibility), or
IllegalArgumentExceptions, if you try and access the field on an object not of the field’s class’s type:
f.get("BOB"); //will throw IllegalArgumentException, as String is of the wrong type