How detect method calls that are not already in 1.4

Question

My program is compiled with JDK 1.5 or 1.6 and retroweaved to 1.4.
If I do not take care I may type
int i=65;
Character.isDigit(i);
instead of
Character.isDigit(char)i);
Without casting to char it uses a method that exists only since 1.5 but not
yet in 1.4.
There are a few other methods that had been added since 1.5
Their use leads to NoSuchMethodError on 1.4 clients.
Their usage must be avoided.
How can I recognize them at compile time?
Or has anybody written a tool to check all method calls
whether they already exist in 1.4 ?
If not I would write it myself and probably will use the javap output.
After reading through the docs of java.lang.reflect.Method I guess that
there is no flag telling when a method had been introduced.

Answer 1

there was some discussion on that here:
http://forum.java.sun.com/thread.jspa?threadID=586602
If you use ant, you could also try and configure the src and target properties of javac task:
http://ant.apache.org/manual/CoreTasks/javac.html
Alper