code: public void hardKill() {
      checkStarted();
      if (isRunning()) {
        if (this.processId != 0) {
          try {
            if (this.isExecuteAsUser) {
              final String cmd =
                  String.format("%s %s %s -9 %d", this.executeAsUserBinary,
                      this.effectiveUser, KILL_COMMAND, this.processId);
              Runtime.getRuntime().exec(cmd);
            } else {
              final String cmd = String.format("%s -9 %d", KILL_COMMAND, this.processId);
              Runtime.getRuntime().exec(cmd);
            }
          } catch (final IOException e) {
            this.logger.error("Kill attempt failed.", e);
          }
        }
        this.process.destroy();
      }
    }
docs: Force kill this process