Integer 为空赋值给int

今天遇到了一个异常，将Integer的值赋值给int时不会自动将Integer 的null转化为0，而是报运行时异常，空指针

 public static void main(String[] args) throws Exception { 
          Integer i = null;
          test(i);
          System.out.print(i);
      } 

      public static void test(int i){
          System.out.print(i);
          int n = 0;
          n = i;
          System.out.print(n);
      }





public static void main(String[] arg){
        int i = 0;
        test(i);

        Map<Long,Integer> map = new HashMap<Long,Integer>();
        map.put((long) 1, null);

        test2(map.get(1));
    }
    public static void test(Integer id){
        System.out.print("+++++++++++++++++" +   id);
    }

    public static void test2(Integer id){
        int i = id;
        System.out.print(id);
    }