code: public synchronized static BshClassPath getBootClassPath()
          throws ClassPathException
      {
          if ( bootClassPath == null )
          {
              try
              {
                  bootClassPath = new BshClassPath(
                          "Boot Class Path", new URL[] { getRTJarPath() } );
              } catch ( MalformedURLException e ) {
                  throw new ClassPathException(" can't find boot jar: "+e, e);
              }
          }
          return bootClassPath;
      }
docs: Get the boot path including the lib/rt.jar if possible.