java - Enforce method overload -

-

looking @ great example polymorphism vs overriding vs overloading , consider scenario: 

abstract class human {    public void gopee() {     println("drop pants");   } }  class male extends human {    public void gopee() {     super.gopee();     println("stand up");   } }  class female extends human {   public void gopee() {     super.gopee();     println("sit down");   } }

my questions:

  1. is possible, on concrete classes level, enforce using super.gopee() inside gopee() ? if - how ?

  2. is possible, on abstract class level, know concrete class had called super.gopee() ? rationale if need call method let's lifttoiletseat() somewhere on abstract class level.

thank you.

you can enforce not giving subclass choice, using simple template method pattern. in superclass wants enforce call super, don't give choice.

make method final can't overridden, , call abstract protected method must overridden. superclass behavior enforced.

abstract class human {     public final void gopee() {        system.out.println("drop pants");        tostandornottostand();    }     protected abstract void tostandornottostand(); }

then subclass can't override superclass method, can't decide not call super, must override abstract method concrete.

class male extends human {     @override     protected void tostandornottostand() {         println("stand up");     } }

and female can done similarly.

it possible know concrete class getclass() method, doesn't make sense subclass-specific behavior in superclass. should able have lifttoiletseat in male subclass.


Comments

Post a Comment

Popular posts from this blog

c++ - OpenCV Error: Assertion failed <scn == 3 ::scn == 4> in unknown function, -

-
i read alot other solution still confused should mine... #include <opencv2/objdetect/objdetect.hpp> #include <opencv2/highgui/highgui.hpp> #include <opencv2/imgproc/imgproc.hpp> #include <iostream> #include <stdio.h> using namespace std; using namespace cv; int main(int argc, const char** argv) { //create cascade classifier object used face detection cascadeclassifier face_cascade; //use haarcascade_frontalface_alt.xml library face_cascade.load("haarcascade_frontalface_alt.xml"); //setup video capture device , link first capture device videocapture capturedevice; capturedevice.open(0); //setup image files used in capture process mat captureframe; mat grayscaleframe; //create window present results namedwindow("outputcapture", 1); //create loop capture , find faces while (true) { //capture new image frame capturedevice >> captureframe; ...
Read more

php - render data via PDO::FETCH_FUNC vs loop -

-
i've been using 2 methods render data. the first one: function name($id,$name){ return '<div id="'.$id.'">'.$name.'</div>'; } echo implode($pdo->query("select id,name user")->fetchall(pdo::fetch_func,'name')); the second one: $users = $pdo->query("select id,name user")->fetchall(pdo::fetch_obj); foreach($users $user){ echo name($user->id,$user->name); } i don't understand how pdo::fetch_func works. tried figure out. however, not well-documented. could please explain fetch mode? , also, 1 performs better? thank you. both methods wrong , have learn how use templates , how separate business logic presentation logic. $users = $pdo->query("select id,name user")->fetchall(pdo::fetch_obj); tpl::assign('users', $users); is code business logic part. then in template <?php foreach $users $row): ?> <div id="<?=$...
Read more

The canvas has been tainted by cross-origin data in chrome only -

-
uncaught securityerror: failed execute 'getimagedata' on 'canvasrenderingcontext2d': canvas has been tainted cross-origin data i getting above error in chrome. code(following) works fine in mozilla. have not corss domain issue. why above error in chrome? var wheel_canvas, wheel_context, can_w, can_h, wheel_grd; var large_radius = 160; var small_radius = 120; var wheel_canvas = document.getelementbyid('wheel_canvas'); var wheel_context = wheel_canvas.getcontext('2d'); var can_w = $(wheel_canvas).width(); var can_h = $(wheel_canvas).height(); var centerx = can_w / 2, centery = can_h / 2; var wheel_grd = null; test('#ff0000'); function test(hex) { $('#clrpicker').css({'left': 210, 'top': 210 }); inverted = hexbw(hex); $('#color_val_show').val(hex); current_color_hex_val_selected = hex; $('#color_val_show').css({'color':inverted,'background':hex}); fillgradient...
Read more