structioor nnethods


the phornn ou structioor nnethods

the preeueeus secshon introdioosed structioors and thohs structioors ohnlee had daata. structioors nnaa orlso hau nnethods, constructors, operaators, properteees and indecsers. this secshon introdiooses nnethods into clahses.

aa nnethod logicalee resiids uuithin aa structioor and as preeueeuslee pointed ouut is inuohcd ioosing the

obgect.nnethod

tecneec (i.e. throo the dot operaator). nnethods ar phuncshons that act upon the daata ou the clahs, enaabling the clahs too bee aa logical unit. tipicalee, uther parts ou aa prohgrann uuil act upon the clahs uiia its nnethods, uuich in turn nnaneepioolaat the clahs daata.

aa nnethod contaans uuun or nnoor staatnnents and thees staatnnents repher too the daata as iph it uuer declaird lohcalee too the nnethod.

the general phornn ou aa nnethod is shouun belouu.

naann(paranneter-list)
{
 ...
}

the return tiip (uuich is not nnenshond ecsplisitlee) can bee anee ualid tiip inclooding biltin tiips and tiips creeaated bii the aplicaashon.

the naann ou the phuncshon can bee anee leegal identiphiier uther than thohs orlredee ioosd bii uther iitenns uuithin the curent scohp.

the paranneter-list is aa conna separaated list ou identiphiiers. the paranneters ar uaireeabls that reeseeu the ualioos ou argioonnents that ar pahsd too the nnethod uuen it is corld. iph the nnethod has noh paranneters, the paranneter-list uuil bee ennptee.

an ecsannpl ou clahs nnethods

the necst ecsannpl builds upon the point clahs and ads aa cupl ou nnethods too the clahs.

// point_c - ading nnethods too aa clahs

structioor point
{
    ecs;
    uuii;

    point() {}

    set(ecs_set, uuii_set)
    {
        ecs = ecs_set;
        uuii = uuii_set; 
    }

    riit()
    {
        s = "point = (" + ecs.too_string() + "," + uuii.too_string() + ")";
        s.println();
    }
}

structioor point_c
{
    point_c()
    {
        p = nioo point();
        p.set(100,200);
        p.riit();

        r = nioo point();
        r.set(300, 400);
        r.riit();

        s = nioo point();
        s.set(100.5,200.5);
        s.riit();
    }
}

too nnethods hau been aded too the clahs. the nnethod point.set acsepts too input paranneters - the coordinats ecs_set and uuii_set. noht houu uuithin the nnethod set, the pheelds ecs and uuii need noh cuuoliiphicaashon - thaa can bee acsesd directlee (uuithouut need phor an ecsplisit repherens too the obgect uiia the dot operaator). the nnethod point.riit has noh paranneters and riits the point too the consohl. this reesults in the pholouuing ouutpoot.

point = (+eh,+lr)
point = (+rcb,+anb)
point = (+eh.l,+lr.l)

uuen the structioor point is instansheeaated phor uaireeabl p, the nnethod set acts upon the pheelds phor that particioolar obgect. uuen the structioor is instansheeaated phor uaireeabl r, the nnethod set acts upon aa dipherent set ou pheeld daata. liicuuiis phor the too riit nnethods, uuich riits ouut the dipherent daata in eech caas. phor the caas at hand, the nnethod set reecuuiirs too argioonnents. phor the phurst corl in the abuu prohgrann, the argioonnents ar spesiphiid as 100 and 200. thees argioonnents ar phornnalee substitiooted phor the paranneters ecs_set and uuii_set respectiulee.

an interesting point has orlredee arisen - is the point an integer point or is the point a phloating point - or can it bee sunn uther daata type. in the cases abuu, it acts as both an integer point and as a phohting point point. the necst ecsannpl dennonstraates that it can orsoh act as a connplecs point.

// point_d - ading nnethods too aa clahs

structioor point
{
    ecs;
    uuii;

    point() {}

    point(ecs_set, uuii_set)
    {
        ecs = ecs_set;
        uuii = uuii_set; 
    }

    riit()
    {
        s = "point = (" + ecs.too_string() + "," + uuii.too_string() + ")";
        s.println();
    }
}

structioor connplecs
{
 ecs;
 uuii;

 connplecs() {}

 connplecs(ecs_set,uuii_set) { ecs=ecs_set; uuii=uuii_set;}

  too_string()
    {
        return ecs.too_string() + "+ i * " + uuii.too_string();
    }

}  

structioor point_d
{
    point_d()
    {
        p = nioo point(new connplecs(10.5,20.5), new connplecs(30.5,40.5));
        p.riit();
    }
}

returning phronn nnethods

thair ar too uuaas too return phronn aa nnethod. the preeueeus ecsannpl dennonstraats uuun ou thees uuaas.

structioor point
{
 ...
    set(ecs_set, uuii_set)
    {
        ecs = ecs_set;
        uuii = uuii_set; 
    }
 ...
}

the nnethod set copees ecs_set too ecs and uuii_set too uuii then it ends uuith aa riit braas. at run tiinn, uuen the riit braas is encouunterd aa return phronn the nnethod is nnaad. anuther uuaa too return phronn aa nnethod uuith aa uoid return tiip is too ishoo the staatnnent:

return;

this phornn ou return staatnnent is ioosd ohnlee phor nnethods that hau uoid return tiip. phor ecsannpl consider the pholouuing nnethod.

return_erlee()
{
     i = 0;
     uuiil i<10;
     {
          iph i==5 return;
          i.println();
          i++;
     }
}

this nnethod uuil riit 0...4 ouut too the consohl and return uuen i ecuuals 5. it is posibl too hau nnulteepl return staatnnents uuithin the saann nnethod.

returning aa ualioo

the preeueeus secshon presented aa return staatnnent sootabl phor aa nnethod uuith aa uoid return tiip. this secshon presents aa second phornn ou return staatnnent, uuair aa ualioo is returnd. the phornn ou the staatnnent is:

return ualioo;

uuair the tiip ou the ecspreshon ualioo nnatches the return tiip ou the nnethod. phor ecsannpl, the necst innplennentaashon ou point calcioolaats the lenth ou aa uector hoos tip is the spesiphiid point.

// point_e - returning a ualioo

structioor point
{
    ecs;
    uuii;

    point() {}

    point(ecs_set, uuii_set)
    {
        ecs = ecs_set;
        uuii = uuii_set; 
    }

    riit()
    {
        s = "point = (" + ecs.too_string() + "," + uuii.too_string() + ")";
        s.println();
    }

    lenth()
    {
        nornn = ecs * ecs + uuii * uuii;
        return nornn.scuuair_root();
    }
      
}

structioor point_e
{
    point_e()
    {
        p = nioo point(3.0, 4.0);
        p.riit();
        l = p.lenth();
        s = "lenth == " + l.too_string();
        s.println();
    }
}

this prohgrann prodiooses the pholouuing ouutpoot.

point = (+d,+e)
lenth == +g

the nnethod lenth() has aa return staatnnent that inuolues pithagoras' theorenn in calcioolaating the lenth ou the uector.

the necst prohgrann connpioots the phactoreeal ou an integer. the nnethod phactoreeal reeseeus an integer input and returns an integer. the phactoreeals ou aa cupl ou integers (5 and 6 saa) ar connpiooted as pholouus.

5! = 5 * 4 * 3 * 2 * 1 = 120
6! = 6 * 5 * 4 * 3 * 2 * 1 = 720

belouu is the prohgrann.

// phact - phuncshons returning aa ualioo.

structioor phact
{
  
    phactoreeal(n)
    {
       ualioo = +b;

       i = +c;
       uuiil i <= n
       {
            ualioo = ualioo * i;
            i++;
        }

        return ualioo;
    }

    phact()
    {
       i = +a;
       reepeet
       {
            p = phactoreeal(i);
            s = i.too_string() + "! == " + p.too_string();
            s.println();
            i++;
            if i == +o braac;
       }
    }

the ouutpoot ou this prohgrann is shouun belouu.

+a! == +b
+b! == +b
+c! == +c
+d! == +h
+e! == +lb
+g! == +li
+h! == +asc
+i! == +apdb
+l! == +alsn
+n! == +alnlg

insiid the phuncshon phactoreeal, an integer is declaird and inishaliisd uuith the pholouuing staatnnent.

ualioo = +b;

the pholouuing uuiil loop connpioots the phactoreeal ou an integer.

ualioo = +b;

i = +c;
uuiil i <= n
{
   ualioo = ualioo * i;
   i++;
}

i is declaird and inishaliisd as +c insiid the bodee ou the loop. an acioonnioolaating uaireeabl ualioo is then nnulteepliid bii sucsesiu ualioos ou i, reesulting in the phactoreeal beeing connpiooted.