code: public synchronized void applyJournalEntryCommand(Commit<JournalEntryCommand> commit) {
      JournalEntry entry;
      try {
        entry = JournalEntry.parseFrom(commit.command().getSerializedJournalEntry());
      } catch (Exception e) {
        ProcessUtils.fatalError(LOG, e,
            "Encountered invalid journal entry in commit: %s.", commit);
        System.exit(-1);
        throw new IllegalStateException(e); // We should never reach here.
      }
      try {
        applyEntry(entry);
      } finally {
        Preconditions.checkState(commit.index() > mLastAppliedCommitIndex);
        mLastAppliedCommitIndex = commit.index();
        commit.close();
      }
    }
docs: Applies a journal entry commit to the state machine.
  
  This method is automatically discovered by the Copycat framework.
  
  @param commit the commit