After dealing with several recent multi-threaded JSSE escalations, we should really rework our debug output to be clearer what is being output, and when. Currently we just call System.out repeatedly. This has at least two issues:

1) It's hard to know which thread is calling.
2) Many related calls to System.out.println can interleaved. We should consider creating a large StringBuffer, then outputing that all at once.

For example:

        if (debug != null && Debug.isOn("verbose")) {
            s.print("RandomCookie: ");
            clnt_random.print(s);

            s.print("Session ID: ");
            s.println(sessionId);

            s.println("Cipher Suites: " + cipherSuites);

            Debug.println(s, "Compression Methods", compression_methods);
            extensions.print(s);
            s.println("***");

This will take a fair amount of work, but will definitely help in the debugging.
Also, it would be good for binary data to be output as hex numbers instead of signed decimals. This will make it easier to match up tcpdump/snoop data fields.