code: public synchronized int getTransactionIsolation() throws SQLException {
  
          checkClosed();
  
          try {
              return sessionProxy.getIsolation();
          } catch (HsqlException e) {
              throw Util.sqlException(e);
          }
      }
docs: <!-- start generic documentation -->
  
  Retrieves this <code>Connection</code> object's current
  transaction isolation level.
  
  <!-- end generic documentation -->
  <!-- start release-specific documentation -->
  <div class="ReleaseSpecificDocumentation">
  <h3>HSQLDB-Specific Information:</h3> <p>
  
  HSQLDB 2.0 supports all isolation levels. If database transaction
  control is MVCC, <code>Connection.TRANSACTION_READ_UNCOMMITED</code>
  is promoted to <code>Connection.TRANSACTION_READ_COMMITED</code>.
  
  </div> <!-- end release-specific documentation -->
  
  @return the current transaction isolation level, which will be one
  of the following constants:
  <code>Connection.TRANSACTION_READ_UNCOMMITTED</code>,
  <code>Connection.TRANSACTION_READ_COMMITTED</code>,
  <code>Connection.TRANSACTION_REPEATABLE_READ</code>,
  <code>Connection.TRANSACTION_SERIALIZABLE</code>, or
  <code>Connection.TRANSACTION_NONE</code>.
  @exception SQLException if a database access error occurs
  (JDBC4 Clarification:)
  or this method is called on a closed connection
  @see JDBCDatabaseMetaData#supportsTransactionIsolationLevel
  @see #setTransactionIsolation