android - If / else statement doing the opposite of what is expected (code + exaplanations) -

i experiencing not emergency problem application works however, understand why behaving this.
there in program method (findfilterintable) 2 string inputs (categoryinterval , paymentinterval).

the method sending request database, finding elements in columns categoryinterval = , paymentinterval = (depending on buttons clicked, choices of user, , on).

there in application radiobutton setting value of paymentinterval :

onclicklistener radiobutton_no_listener = new onclicklistener() {     public void onclick(view v) {         paymentinterval = null ;      } };  onclicklistener radiobutton_yes_listener = new onclicklistener() {     public void onclick(view v) {         paymentinterval = " " + " '%visa%' " ;          } }; 

so when user clicks button no, means paymentinterval null.

now, here method querying database. crashing while making request in col_payment when paymentinterval null, want change query : if paymentinterval null, not query related column in database (col_payment). , else (if paymentinterval isn't null), query col_payment , collect results.
tried way, didn't work , in despair exchanged statement , works :

 public cursor findfilterintable(string categoryinterval,         string paymentinterval) {     string where;     if (paymentinterval != null) {         = "(" + col_cat1 + " in " + categoryinterval + " or "                 + col_cat2 + " in " + categoryinterval + " or " + col_cat3                 + " in " + categoryinterval + ") , (" + col_payment                 + paymentinterval + ") ";     }      else {         = col_cat1 + " in " + categoryinterval + " or " + col_cat2                 + " in " + categoryinterval + " or " + col_cat3 + " in "                 + categoryinterval;     }      cursor c = mydatabase.query(database_table, new string[] { key_rowid,             col_name, col_street, col_website, col_payment, col_telephone,             col_price, col_remarks, col_datefriendly }, where, null, null,             null, null);     return c; } 

this code works , opposite of written. when use application:
- if paymentinterval null (the user clicks no), doesn't query col_payment
- if paymentinterval isn't null (and %visa% in case), query database , display right results.

do know causes weird results ?

[edit] listener attached buttons :

radiobutton_yes = (radiobutton) dialogview                 .findviewbyid(r.id.radiobutton_yes);         radiobutton_yes.setonclicklistener(radiobutton_yes_listener);          radiobutton_no = (radiobutton) dialogview                 .findviewbyid(r.id.radiobutton_no);         radiobutton_no.setonclicklistener(radiobutton_no_listener); 

this code written.

if (paymentinterval != null) 

!= is not equal operator. so, if paymentinterval not equal null, adds col_payment query; else leaves out.