You can use DBMS_SQL Package for this:
DECLARE
stmt DBMS_SQL.VARCHAR2A;
c number;
res number;
BEGIN
stmt(1) := 'create view view_a (';
stmt(2) := 'col_a, ';
stmt(3) := 'col_b, ';
stmt(4) := 'col_c) as '
stmt(5) := 'select ';
stmt(6) := 'col_bb, ';
stmt(7) := 'col_cc + col_ee + DECODE(...), ';
stmt(8) := 'col_dd) ';
stmt(9) := 'from table_b ';
stmt(10) := 'where ... ';
-- each element can have up to 32K characters, number of elements is (almost) unlimited
c := DBMS_SQL.open_cursor;
DBMS_SQL.parse(c, stmt, 1,10, TRUE, DBMS_SQL.NATIVE);
res := DBMS_SQL.execute(c);
DBMS_SQL.close_cursor(c);
END;