code: public synchronized Object firstKey(Transaction transaction)
                      throws ObjectManagerException
      {
          if (Tracing.isAnyTracingEnabled() && trace.isEntryEnabled())
              trace.entry(this,
                          cclass,
                          "firstKey",
                          new Object[] { transaction });
          Entry entry = firstEntry(transaction);
          Object returnKey = entry.getKey();
  
          if (Tracing.isAnyTracingEnabled() && trace.isEntryEnabled())
              trace.exit(this,
                         cclass,
                         "firstKey",
                         new Object[] { returnKey });
          return returnKey;
      }
docs: Returns the first (lowest) key currently in this sorted map
  which is visible to the transaction.
  
  @param transaction the transaction which determines the first visible key.
  @return the first (lowest) key currently in this sorted map.
  @exception ObjectManagerException