code: public DefaultReconfigurationProblem build() throws SchedulerException {
  
          if (runs == null) {
              //The others are supposed to be null too as they are set using the same method
              Mapping map = model.getMapping();
              runs = new HashSet<>();
              sleep = new HashSet<>();
              for (Node n : map.getOnlineNodes()) {
                  runs.addAll(map.getRunningVMs(n));
                  sleep.addAll(map.getSleepingVMs(n));
              }
              waits = map.getReadyVMs();
              over = Collections.emptySet();
          }
  
          if (manageable == null) {
              manageable = new HashSet<>();
              manageable.addAll(model.getMapping().getSleepingVMs());
              manageable.addAll(model.getMapping().getRunningVMs());
              manageable.addAll(model.getMapping().getReadyVMs());
          }
  
          if (ps == null) {
              ps = new DefaultParameters();
          }
          return new DefaultReconfigurationProblem(model, ps, waits, runs, sleep, over, manageable);
      }
docs: Build the problem
  
  @return the builder problem
  @throws org.btrplace.scheduler.SchedulerException if an error occurred