oracle create index if not exists

1DECLARE
2    already_exists EXCEPTION;
3    columns_indexed EXCEPTION;
4    PRAGMA EXCEPTION_INIT ( already_exists, -955 );
5    PRAGMA EXCEPTION_INIT (columns_indexed, -1408);
6BEGIN
7    EXECUTE IMMEDIATE 'CREATE INDEX ord_customer_ix ON orders (customer_id)';
8    dbms_output.put_line('created');
9EXCEPTION
10    WHEN already_exists OR columns_indexed THEN
11        dbms_output.put_line('skipped');
12END;