code: public final void setDefaultTransactionIsolation(final int defaultTransactionIsolation) {
  
          if (defaultTransactionIsolation != Connection.TRANSACTION_NONE
                  && defaultTransactionIsolation != Connection.TRANSACTION_READ_COMMITTED
                  && defaultTransactionIsolation != Connection.TRANSACTION_READ_UNCOMMITTED
                  && defaultTransactionIsolation != Connection.TRANSACTION_REPEATABLE_READ
                  && defaultTransactionIsolation != Connection.TRANSACTION_SERIALIZABLE
                  ) {
              throw new IllegalArgumentException("TransactionIsolation level must be one of the JDBC supported levels");
          }
  
          // no need for defensive copies of int
  
          this.defaultTransactionIsolation = defaultTransactionIsolation;
      }
docs: The default TransactionIsolation state of connections created by this pool.
  <p>
  The following values are allowed:
  <ul>
  <li>Connection.TRANSACTION_NONE</li>
  <li>Connection.TRANSACTION_READ_COMMITTED</li>
  <li>Connection.TRANSACTION_READ_UNCOMMITTED</li>
  <li>Connection.TRANSACTION_REPEATABLE_READ</li>
  <li>Connection.TRANSACTION_SERIALIZABLE</li>
  </ul>
  
  @param defaultTransactionIsolation The default TransactionIsolation state of connections created by this pool
  @see java.sql.Connection