有关声明和初始化的问题

Question

我对初始化有疑问。当我们使用{}初始化数组时，必须在声明后立即执行以显示编译器要使用的类型。为什么编译器允许Diamond运算符使用2条语句来做到这一点？

Integer[] array = {2,4,5};
//Integer[] array; array = {2,4,5}; - error
List<Integer> list = new ArrayList<>();
//List<Integer> list; list = new ArrayList<>(); - no error

Answer 1

您也可以对数组进行两行处理，只需在初始化时创建一个新对象（当然也要明确指定类型）。

public class PersonDto
  {
    private Status status;
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string Surname { get; set; }

    public Status LivingStatus
    {
      get => status;

      set
      {
        status = value;

        switch (status)
        {
          case Status.Homeowner:
            IsHomeOwner = true;
            IsTenant = false;
            IsLivingWithParents = false;
            break;

          case Status.LivingWithParents:
            IsHomeOwner = false;
            IsTenant = false;
            IsLivingWithParents = true;
            break;

          case Status.Tenant:
            IsHomeOwner = false;
            IsTenant = true;
            IsLivingWithParents = false;
            break;

          default:
            throw new ArgumentOutOfRangeException();
        }
      }
    }


    public bool IsHomeOwner { get; set; }
    public bool IsTenant { get; set; }
    public bool IsLivingWithParents { get; set; }
  }