将 List<Object[]> 转换为 List<MyClass>

Question

 List<Object[]> listChild = query.list();

 List<ChildrenDTO> listOfDTO = new ArrayList<>();

 //Loop through arraylits of object

 for(Object[] org: listOrg){

      //How to cast List of object to ist<ChildrenDTO>?

     listOfDTO.add(org);

 }

我正在遍历对象列表并需要返回 listOfDTO。如何将列表转换为列表？

Answer 1

如果您使用 java 8，则应该尝试使用流 api。考虑到 DTO 的构造函数有一个String参数。List<Object[]> listChild = query.list();List<ChildrenDTO> children = listChild.stream().map(x -> new ChildrenDTO(x[0].toString())).collect(Collectors.toList());

Answer 2

因此，首先，您要遍历包含对象数组的 List。因此，要获取每个单独的对象，您需要有一个嵌套循环，例如：&nbsp; &nbsp; &nbsp; &nbsp; for (Object[] org : listOrg) {&nbsp; &nbsp; &nbsp; &nbsp; for (int i = 0; i < org.length; i++) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (org[i] instanceof ChildrenDTO) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; listOfDTO.add((ChildrenDTO) org[i]);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }我不是 100% 确定您是否可以将对象强制转换为 ChildrenDTO 对象，但如果不能，您可以只获取对象值并创建一个新的 ChildrenDTO 实例，也许是一个构造函数来获取对象值？

Answer 3

您可以使用Java 8 流 API：List<Object[]>&nbsp;listChild&nbsp;=&nbsp;...List<ChildrenDTO>&nbsp;childrenDtos&nbsp;=&nbsp;listChild.stream() &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.flatMap(Arrays::stream) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.filter(object&nbsp;->&nbsp;Objects.equals(object.getClass(),ChildrenDTO.class)) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//.filter(object&nbsp;->&nbsp;object&nbsp;instanceof&nbsp;ChildrenDTO)&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//instead&nbsp;of&nbsp;Objects.equals(class,&nbsp;class),&nbsp;if&nbsp;required &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.map(object&nbsp;->&nbsp;(ChildrenDTO)object) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.collect(Collectors.toList());