code: @Override
      public CheckSum generateCheckSum() {
          InputStream stream = null;
          try {
              stream = openSqlStream();
  
              String sql = this.sql;
              if ((stream == null) && (sql == null)) {
                  sql = "";
              }
  
              if (sql != null) {
                  stream = new ByteArrayInputStream(
                      sql.getBytes(
                          LiquibaseConfiguration.getInstance().getConfiguration(GlobalConfiguration.class)
                          .getOutputEncoding()
                      )
                  );
              }
  
              return CheckSum.compute(new NormalizingStream(this.getEndDelimiter(), this.isSplitStatements(), this.isStripComments(), stream), false);
          } catch (IOException e) {
              throw new UnexpectedLiquibaseException(e);
          } finally {
              if (stream != null) {
                  try {
                      stream.close();
                  } catch (IOException e) {
                      Scope.getCurrentScope().getLog(getClass()).fine(LogType.LOG, "Error closing stream", e);
                  }
              }
          }
      }
docs: Calculates the checksum based on the contained SQL.
  
  @see liquibase.change.AbstractChange#generateCheckSum()