code: public void setActiveInstances(java.util.Collection<ActiveInstance> activeInstances) {
          if (activeInstances == null) {
              this.activeInstances = null;
              return;
          }
  
          this.activeInstances = new com.amazonaws.internal.SdkInternalList<ActiveInstance>(activeInstances);
      }
docs: <p>
  The running instances. This list is refreshed periodically and might be out of date.
  </p>
  
  @param activeInstances
  The running instances. This list is refreshed periodically and might be out of date.