code: public String fillLockMutation(MutationBatch m, Long time, Integer ttl) {
          if (lockColumn != null) {
              if (!lockColumn.equals(prefix+lockId))
                  throw new IllegalStateException("Can't change prefix or lockId after acquiring the lock");
          }
          else {
              lockColumn = prefix + lockId;
          }
          
          Long timeoutValue 
                = (time == null)
                ? new Long(0)
                : time + TimeUnit.MICROSECONDS.convert(timeout, timeoutUnits);
                
          m.withRow(columnFamily, key).putColumn(lockColumn, generateTimeoutValue(timeoutValue), ttl);
          return lockColumn;
      }
docs: Fill a mutation with the lock column. This may be used when the mutation
  is executed externally but should be used with extreme caution to ensure
  the lock is properly released
  
  @param m
  @param time
  @param ttl