Re: Invoking ArrayList.get() impossible with reflection ?

From:

Joshua Cranmer <Pidgeot18@verizon.invalid>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 19 Sep 2008 10:29:07 -0400

Message-ID:

<gb0cvj$392$1@news-int.gatech.edu>

S?bastien de Mapias wrote:

I get the following in both cases (the *same* output):
~ OK METHOD NAME trimToSize
~ FAILS FOR ensureCapacity
~ OK METHOD NAME size
~ OK METHOD NAME isEmpty
~ FAILS FOR contains
~ FAILS FOR indexOf
~ FAILS FOR lastIndexOf
~ OK METHOD NAME clone
~ OK METHOD NAME toArray
~ FAILS FOR toArray
~ FAILS FOR get
~ FAILS FOR set
~ FAILS FOR add
~ FAILS FOR add
~ FAILS FOR remove
~ FAILS FOR remove
~ FAILS FOR fastRemove
~ OK METHOD NAME clear
~ FAILS FOR addAll
~ FAILS FOR addAll
~ FAILS FOR removeRange
~ FAILS FOR RangeCheck
~ FAILS FOR writeObject
~ FAILS FOR readObject

Notice anything about the methods that succeed and the ones that fail?
Let's look at the Javadocs for select ones:

void trimToSize();
[ ensureCapacity isn't in there... it's a private method, so you
violated an access constraint. ]
int size()
boolean isEmpty()
boolean contains(Object o)
int indexOf(Object o)
int lastIndexOf(o)
....

Hey, there's a pattern! This fails for
a. Non publicly accessible methods and
b. Methods with arguments.

What you want to do is you want to pass the parameters into invoke, e.g.,

invoke(ref, 0) for a 1-arg method, or
invoke(ref, 5, null) for a 2-arg method, etc.

--
Beware of bugs in the above code; I have only proved it correct, not
tried it. -- Donald E. Knuth