com.sun.tools.javac.Launcher is not part of the JDK as specified in the class
description:

   This class is not available in the JDK. It is not
   compiled by default and will not be in tools.jar.

However, this class is unexpectedly included in JDK 7 tools.jar:

$ jar tvf /java/re/jdk/7/latest/binaries/solaris-i586/lib/tools.jar | grep com.sun.tools.javac.Launcher
  1421 Mon Jun 27 02:22:06 PDT 2011 com/sun/tools/javac/Launcher.class