如何在java中将字符串数组元素添加到arraylist

Question

How do I add string array elements to an arraylist?

  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    List<BudgetEntity> budgetEntityList = new ArrayList<>(20); 
    BudgetEntity budgetEntity = new BudgetEntity();

    String budgetID[] = request.getParameterValues("budgetID");

for(int i=0;   i < budgetID.length ;   i++) {

      for(int k=0;   k < budgetEntityList.size() ;   k++) {

          budgetEntity=  budgetEntityList.get(k);
      }

            budgetEntity.setTotal(Integer.valueOf(budgetID[i]));
        }

Answer 1

Your budgetEntityList is empty when you do budgetEntity= budgetEntityList.get(k);

Doing a new ArrayList<>(capacity) does not fill your ArrayList with BudgetList objects, it only sets the initial capacity of your ArrayList.

So, what you need to do is:

 for(int k=0;   k < budgetEntityList.size() ;   k++) {
      budgetEntity = new BudgetEntity();
      budgetEntityList.add(budgetEntity);
  }

And then, set the total of your BudgetEntity