code: public boolean setMainKey(boolean bDisplayOption, Boolean boolSetModified, boolean bSetIfModified)
      {
          super.setMainKey(bDisplayOption, boolSetModified, bSetIfModified);
          boolean bNonNulls = false;  // Default to yes, all keys are null.
          if (m_fldThisFile != null)
          {
              m_fldThisFile.setString(m_strFirst, bDisplayOption, DBConstants.READ_MOVE);     // Set the booking number in pax file
              if (!m_fldThisFile.isNull())
                  bNonNulls = true;   // Non null.
          }
          if (m_fldThisFile2 != null)
          {
              m_fldThisFile2.setString(m_strSecond, bDisplayOption, DBConstants.READ_MOVE);
              if (!m_fldThisFile2.isNull())
                  bNonNulls = true;   // Non null.
          }
          if (m_fldThisFile3 != null)
          {
              m_fldThisFile3.setString(m_strThird, bDisplayOption, DBConstants.READ_MOVE);
              if (!m_fldThisFile3.isNull())
                  bNonNulls = true;   // Non null.
          }
          return bNonNulls;
      }
docs: Setup the target key field to the initial string values.
  @oaram bDisplayOption If true, display changes.
  @param boolSetModified - If not null, set this field's modified flag to this value
  @return false If this key was set to all nulls.