java - Painting array of constant size? -

-

i having trouble doing simple, painting array of elements. here have paint method in class array: (xb , yb x , y values want increment make instances show in different locations).

public void paint(graphics pane) {     private box[] boxes = new box[num_box];      for(int = 0; i<num_box; i++){         if (xb == 290){             xb = 0;             yb = yb + 20;         }          boxes[i].paint(pane, xb, yb);         xb = xb + 20;     }

and here have in box class being painted:

public class box {      private final int width = 20;     private final int height = 20;     private boolean = true;      public void paint(graphics pane, int x, int y) {             pane.setcolor(color.black);                  pane.drawrect(x, y, width, height);          pane.setcolor(color.gray);                    pane.fill3drect(x +2, y+2, width - 3, height - 3, up);       } }

every time run it, tells me there nullpointerexception @ boxes[i].paint(pane,xb,yb) line. doing wrong?


Comments

Post a Comment

Popular posts from this blog

ruby on rails - RuntimeError: Circular dependency detected while autoloading constant - ActiveAdmin.register Role -

-
i using activeadmin , have file doing this: activeadmin.register role something--- end however, server gives me error: runtimeerror: circular dependency detected while autoloading constant role /library/ruby/gems/2.0.0/gems/activesupport-4.0.10/lib/active_support/dependencies.rb:461:in `load_missing_constant' /library/ruby/gems/2.0.0/gems/activesupport-4.0.10/lib/active_support/dependencies.rb:184:in `const_missing' ~/desktop/boxfox/app/admin/role.rb:1:in `<top (required)>' /library/ruby/gems/2.0.0/gems/activesupport-4.0.10/lib/active_support/dependencies.rb:424:in `load' /library/ruby/gems/2.0.0/gems/activesupport-4.0.10/lib/active_support/dependencies.rb:424:in `block in load_file' /library/ruby/gems/2.0.0/gems/activesupport-4.0.10/lib/active_support/dependencies.rb:616:in `new_constants_in' /library/ruby/gems/2.0.0/gems/activesupport-4.0.10/lib/active_support/dependencies.rb:423:in `load_file' /library/ruby/gems/2.0.0/gems/activesuppor...
Read more

c++ - OpenMP unpredictable overhead -

-
i have simple openmp code runs 4 empty threads , reports time: #include "omp.h" #include <sys/time.h> #include <cstdio> double start_time; void process_thread() { } int main(){ struct timeval tv; gettimeofday(&tv, null); start_time = 1000*((double)tv.tv_sec + 1e-6*(double)tv.tv_usec); printf("beginning time: %.3fms ",start_time-start_time); #pragma omp parallel schedule(static,1) for(int i=0;i<4;i++) process_thread(); gettimeofday(&tv, null); double cur_time = 1000*((double)tv.tv_sec + 1e-6*(double)tv.tv_usec); printf("finishing time: %.3fms\n\n",cur_time-start_time); } without openmp running time small , consistent: beginning time: 0.000ms finishing time: 0.050ms beginning time: 0.000ms finishing time: 0.050ms beginning time: 0.000ms finishing time: 0.049ms beginning time: 0.000ms finishing time: 0.049ms beginning time: 0.000ms finishing time: 0.050ms beginnin...
Read more

django rest framework - DRF 3.0: UniqueTogetherValidator with a read-only field -

-
in process of upgrading django rest framework 3.0 2.4.4 , want have read-only user field, failing because 'user' being required uniquetogethervalidator (i think) i have model (excuse typos, simplified , code works fine irl): class examplemodel(models.model): some_attr = models.positivesmallintegerfield() other_attr = models.positivesmallintegerfield() user = models.foreignkey(user) class meta: unique_together = ('some_attr', 'other_attr', 'user') viewset: class exampleviewset(viewsets.modelviewset): queryset = examplemodel.objects.all() serializer_class = exampleserializer def perform_create(self, serializer): serializer.save(user=self.request.user) def perform_update(self, serializer): serializer.save(user=self.request.user) serializer: class exampleserializer(serializers.modelserializer): user = userserializer(read_only=true) class meta: model = examplemodel n...
Read more