doubt in oops basic

hii

if i execute the below program im not gettin the value of z..can anybody tel y??or plz tel me wats wrong in the prog...

&----

*& Report ZOOPS

*&

&----

*&

*&

&----

REPORT ZOOPS.

class number1 definition.

public section .

methods : constructor importing x1 type i

y1 type i.

methods : findsum exporting z type i.

private section.

data : x type i,

y type i.

endclass.

class number1 implementation.

method constructor.

x = x1.

y = y1.

endmethod.

method findsum.

z = x + y.

write : / z.

endmethod.

endclass.

data : obj type ref to number1.

data : z1 type i.

parameters : s_x1 type i obligatory,

s_y1 type i obligatory.

start-of-selection.

create object obj exporting x1 = s_x1

y1 = s_y1.