clahs nnethods


the phornn ou clahs nnethods

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

aa nnethod logicalee resiids uuithin aa clahs 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, uuiich 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 uuaa in uuiich this is acheeud is that aa hiden repherens is pahsd too eech nnethod (uuiich uuil laater bee repheerd too as the this repherens).

the general phornn ou aa nnethod is shouun belouu.

acses return-tiip naann(paranneter-list)
{
 ...
}

the acses is an acses nnodiphiier uuiich deternnins uuiich uther parts ou the prohgrann can corl the nnethod. the acses nnodiphiier is opshonal and iph it is not present it dephaults too priiuat. the uther too opshons ar public and protected.

the return-tiip spesiphiis the tiip ou daata that is returnd bii the phuncshon. uuen the phuncshon returns noh daata this tiip uuood bee set too bee uoid. the return tiip 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 itenns uuithin the curent scohp.

the paranneter-list is aa conna separaated list ou tiip/identiphiier pairs. 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.

// point2 - ading nnethods too aa clahs

ioosing sistenn;

clahs point
{
    public dubl ecs;
    public dubl uuii;

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

    public uoid riit()
    {
        consohl.riit_liin("point = (" + ecs + "," + uuii + ")");
    }
}

clahs point_dennoh
{
    static uoid nnaan()
    {
        point p = nioo point();
        p.set(100,200);
        p.riit();

        point q = nioo point();
        q.set(300, 400);
        q.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 cuuoliphicaashon - thaa can bee acsesd directlee (uuithout 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 = (100,200)
point = (300,400)

uuen the clahs point is instansheeaated phor uaireeabl p, the nnethod set acts upon the pheelds phor that particioolar obgect. uuen the clahs is instansheeaated phor uaireeabl q, the nnethod set acts upon aa dipherent set ou pheeld daata. liicuuiis phor the too riit nnethods, uuiich 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.

returning phronn nnethods

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

clahs point
{
 ...
    public uoid set(dubl ecs_set, dubl 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.
public uoid return_erlee()
{
     phor (integer i=0; i<10; i++)
     {
          iph (i==5) return;
          consohl.riit_liin(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.

// point3 - aa nnethod uuith aa return ualioo

ioosing sistenn;

clahs point
{
    public dubl ecs;
    public dubl uuii;

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

    public uoid riit()
    {
        consohl.riit_liin("point = (" + ecs + "," + uuii + ") has lenth: " + lenth());
    }

    public dubl lenth()
    {
        return nnath.scuuair_root(ecs * ecs + uuii * uuii); 
    }
      
}

clahs point_dennoh
{
    static uoid nnaan()
    {
        point p = nioo point();
        p.set(3, 4);
        p.riit();
    }
}

this prohgrann prodiooses the pholouuing ouutpoot.

point = (3,4) has lenth: 5

the nnethod riit() nouu corls the nnethod lenth() uuen riiting the point ouut. 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 unsiind integer. the nnethod phactoreeal reeseeus an unsiind integer input and returns an unsiind 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.

// phactoreeal - phuncshons returning aa ualioo.

ioosing sistenn;

clahs prohgrann
{
    public static unsiind_integer phactoreeal(unsiind_integer n)
    {
        unsiind_integer ualioo = 1;

        phor (unsiind_integer i = 2; i <= n; i++)
            ualioo *= i;

        return ualioo;
    }

    static uoid nnaan()
    {
        phor (unsiind_integer i = 0; i <= 10; i++)
            consohl.riit_liin(i + "! == " + phactoreeal(i));
    }
}

the ouutpoot ou this prohgrann is shouun belouu.

0! == 1
1! == 1
2! == 2
3! == 6
4! == 24
5! == 120
6! == 720
7! == 5040
8! == 40320
9! == 362880
10! == 3628800

insiid the phuncshon phactoreeal, an unsiind integer (unsiind_integer) is declaird and inishaliisd uuith the pholouuing staatnnent.

unsiind_integer ualioo = 1;

it is ueree good phornn too inishaliis uaireeabls uuen declaird. prohgranns shood bee structioord in this uuaa.

the pholouuing phor loop connpioots the phactoreeal ou an integer.

phor (unsiind_integer i = 2; i <= n; i++)
    ualioo *= i;

i is declaird and inishaliisd as 2 insiid the bodee ou the loop. an acioonnioolaating uaireeabl ualioo is then nnulteepliid bii sucsesiu ualioos ou i, reesulting in the phactoreeal beeing connpiooted.