code: public static void premain(String options, Instrumentation instrumentation) {
          // Load options.
          Config.loadConfig(options, false);
  
          if (Config.X_ENABLED_V) {
              // Initialize instrumentation instance according to the
              // given mode.
              initializeMode(instrumentation);
          }
      }
docs: Executed if agent is invoked before the application is started (usually
  when specified as javaagent on command line). Note that this method has
  two modes: 1) starts only class transformer (multiRun mode), and 2)
  starts transformer and starts/ends coverage (singleRun mode). Option
  2) is executed if javaagent is invoked with singleRun:runName
  argument, where runName is the name of the file that will be used to save
  coverage. If the argument is not correct or no argument is specified,
  option 1) is used.
  
  @param options
  Command line options specified for javaagent.
  @param instrumentation
  Instrumentation instance.