code: public StackSetOperationPreferences withRegionOrder(String... regionOrder) {
          if (this.regionOrder == null) {
              setRegionOrder(new com.amazonaws.internal.SdkInternalList<String>(regionOrder.length));
          }
          for (String ele : regionOrder) {
              this.regionOrder.add(ele);
          }
          return this;
      }
docs: <p>
  The order of the regions in where you want to perform the stack operation.
  </p>
  <p>
  <b>NOTE:</b> This method appends the values to the existing list (if any). Use
  {@link #setRegionOrder(java.util.Collection)} or {@link #withRegionOrder(java.util.Collection)} if you want to
  override the existing values.
  </p>
  
  @param regionOrder
  The order of the regions in where you want to perform the stack operation.
  @return Returns a reference to this object so that method calls can be chained together.