The default AWT and ThreadGroup exception handlers print a message and stack trace to System.err, and then return. The classes in this package replace those, and send the exception information to a Log4J logger.
See information on use in the individual classes.
Java 1.7 removed the separate AWT exception handler set with the sun.awt.exception.handler system property. The AwtHandler was therefore removed from this package for JMRI 4.3.4