refactor: remove ClassCastException catch

CopyManager has two catches for ClassCastException. This ins't very
nice and can easily be changed to do a check before the cast.

closes #527

pgjdbc/src/main/java/org/postgresql/copy/CopyManager.java

@@ -48,26 +48,24 @@ public CopyManager(BaseConnection connection) throws SQLException {
  }

  public CopyIn copyIn(String sql) throws SQLException {
    CopyOperation op = null;
    try {
      op = queryExecutor.startCopy(sql, connection.getAutoCommit());
    CopyOperation op = queryExecutor.startCopy(sql, connection.getAutoCommit());
    if (op == null || op instanceof CopyIn) {
      return (CopyIn) op;
    } catch (ClassCastException cce) {
    } else {
      op.cancelCopy();
      throw new PSQLException(GT.tr("Requested CopyIn but got {0}", op.getClass().getName()),
          PSQLState.WRONG_OBJECT_TYPE, cce);
              PSQLState.WRONG_OBJECT_TYPE);
    }
  }

  public CopyOut copyOut(String sql) throws SQLException {
    CopyOperation op = null;
    try {
      op = queryExecutor.startCopy(sql, connection.getAutoCommit());
    CopyOperation op = queryExecutor.startCopy(sql, connection.getAutoCommit());
    if (op == null || op instanceof CopyOut) {
      return (CopyOut) op;
    } catch (ClassCastException cce) {
    } else {
      op.cancelCopy();
      throw new PSQLException(GT.tr("Requested CopyOut but got {0}", op.getClass().getName()),
          PSQLState.WRONG_OBJECT_TYPE, cce);
              PSQLState.WRONG_OBJECT_TYPE);
    }
  }