Xusage.txt

    -Xmixed           mixed mode execution (default)
    -Xint             interpreted mode execution only
    -Xbootclasspath:<directories and zip/jar files separated by ;>
                      set search path for bootstrap classes and resources
    -Xbootclasspath/a:<directories and zip/jar files separated by ;>
                      append to end of bootstrap class path
    -Xbootclasspath/p:<directories and zip/jar files separated by ;>
                      prepend in front of bootstrap class path
    -Xnoclassgc       disable class garbage collection
    -Xincgc           enable incremental garbage collection
    -Xms<size>        set initial Java heap size
    -Xmx<size>        set maximum Java heap size
    -Xprof            output cpu profiling data
    -Xrunhprof[:help]|[:<option>=<value>, ...]
                      perform JVMPI heap, cpu, or monitor profiling
    -Xdebug           enable remote debugging

The -X options are non-standard and subject to change without notice.