I have create a form. I have write all my business logic in my newly created class. Problem is when I am calling class method in button clicked mthod then it is giving below error


here is my class code
public void parmmethod(str _brand, str _type,
    str _product,int _percentage,
    date _slabstart, date _slabend,
    SL_SchemeCode   _schemecode,
    int64 slabvaluestart, 
    int64 slabvalueend)
{
    brand = _brand;
    type = _type;
    product = _product;
    percentage = _percentage;
    slabstart = slabvaluestart;
    slabend = slabvalueend;
    schemecode = _schemecode;
    fromdate = _slabstart;
    endate = _slabend;
    
    this.insert_header();
    this.insert_line();
}
Below is my button click method code
void clicked()
{
     Args args = new Args();
    RNI_Scheme2 schemeclass = new RNI_Scheme2();
     schemeclass.parmmethod(RNI_Brand.valueStr(),RNI_Type.valueStr(),RNI_Product.valueStr(),
    rni_percentage.value(),any2date(rni_fromdate.valueStr()),any2date(rni_enddate.valueStr()),
    rni_schemecode.valueStr(),
    rni_slabstart.value(),rni_slabend.value());
    //super();
}