How to identify a missing method (Binary Compatibility) in a JAR statically
Clirr - checks Java libraries for binary and source compatibility with older releases:
java -jar clirr-core-0.6-uber.jar -o OLD.jar -n NEW.jar
japi-compliance-checker - backward API/ABI compatibility checker for a Java library:
japi-compliance-checker -lib NAME -old OLD.jar -new NEW.jar
sigtest - Oracle's SigTest signature testing and API conformance tool
japitools - test for compatibility between Java APIs
japi-checker - a java API backward compatibility checker which works at binary level
revapi - API analysis and change tracking tool
or manually using javap decompiler:
javap OLD.class > OLD.txt javap NEW.class > NEW.txt diff -rNau OLD.txt NEW.txt > CHANGES.txt
japicmp is another tool for checking binary compatibility. It is available as standalone command line tool or as maven plugin.
Revapi can do the job, too. It is easy to incorporate it into maven builds, which is not your case obviously, but might be of interest to others.
It can also check arbitrary sets of jars using its standalone mode.