我如何从列表中删除重复记录并用枚举标记它?

Question

解释…我收到两个类型为MyDTO的列表的返回值，并将这两个返回值相加到一个列表中。这些记录被标记，在前两个回报中有一个Enum。由于名单来自不同的地方，我可以有重复的记录。并且，如果有重复记录，我必须在Enum中用特定的类型标记它，并且只留下一条记录。

MyDTO:

@Builder
@AllArgsConstructor
@NoArgsConstructor
@EqualsAndHashCode(exclude = {"myEnum","someField"})
@Getter
@Setter
@ToString
public class MyDTO {
private String someField;
private MyEnum myEnum;
private Long codMyDto;
}

返回类:

@Slf4j
@Singleton
@RequiredArgsConstructor
public class MyCreateContextClass {
@Override
protected List<MyDTO> myMainMethod() throws Exception {
List< MyDTO > myDTOList = new ArrayList<>();
myDTOList.addAll(firstReturnMyDTO());
myDTOList.addAll(secondReturnMyDTO());
// Mark the repeated items with type 3 of the Enum and make them unique.
// How to do that ?
return myDTOList; // My return must have unique items with correct enum
}
private List<MyDTO> firstReturnMyDTO() throws Exception {    
return returnFirstListFromDTO.returnDTO(); // here my Enum is 1
}
private List<MyDTO> secondReturnMyDTO() throws Exception {
return returnSecondListFromDTO.returnDTO(); // here my Enum is 2
}
}

我的枚举:

@Getter
public enum MyEnum {
MYFIRSTYTPE(1, “first”), // first addAll
MYSECONDTYPE(2, “second”), // second addAll
TWORETURNS(3, “all”); // in case the item is on both lists.
private Integer key;
private String value;
MyEnum(Integer key, String value) {
this.key = key;
this.value = value;
}
public static MyEnum getEnum(Integer key) {
for (MyEnum myEnum : MyEnum.values()) {
if (myEnum.getKey().equals(key)) {
return myEnum;
}
}
return MyEnum.MYFIRSTYTPE;
}
}

那么，我如何检查项目是否重复(在两个列表中返回)并将其标记为Enum类型?

Answer 1

使用Java Stream，可以用表示someField和codMyDto的键和收集到set中的枚举来构建映射。之后，映射的条目根据集合的大小/内容被重新映射到MyDto。

protected List<MyDTO> myMainMethod() throws Exception {
return Stream.concat(firstReturnMyDTO().stream(), secondReturnMyDTO().stream())
.collect(Collectors.groupingBy(
dto -> Arrays.asList(dto.getSomeField(), dto.getCodMyDto()), // key w/o enum
Collectors.mapping(MyDto::getMyEnum, Collectors.toSet())
)) // map of List<?> key, Set<MyEnum>
.entrySet().stream()
.map(e -> new MyDto(
e.getKey().get(0), // someField from key
e.getValue().size() > 1 ? MyEnum.TWORETURNS 
: e.getValue().contains(MyEnum.MYSECONDTYPE) ? MyEnum.MYSECONDTYPE
: MyEnum.MYFIRSTTYPE,
e.getKey().get(1) // myCodDto from key 
))
.collect(Collectors.toList());
}

可以使用MyDto作为键，而不是原始列表:

protected List<MyDTO> myMainMethod() throws Exception {
return Stream.concat(firstReturnMyDTO().stream(), secondReturnMyDTO().stream())
.collect(Collectors.groupingBy(
dto -> new MyDto(dto.getSomeField(), null, dto.getCodMyDto()), // key w/o enum
Collectors.mapping(MyDto::getMyEnum, Collectors.toSet())
)) // map of MyDto key with null myEnum, Set<MyEnum>
.entrySet().stream()
.map(e -> new MyDto(
e.getKey().getSomeField(), // someField from key
e.getValue().size() > 1 ? MyEnum.TWORETURNS 
: e.getValue().contains(MyEnum.MYSECONDTYPE) ? MyEnum.MYSECONDTYPE
: MyEnum.MYFIRSTTYPE,
e.getKey().getCodMyDto() // myCodDto from key 
))
.collect(Collectors.toList());
}

Answer 2

像这样?

for(int i = 0; i< list.size(); i++) {
for(int j = i+1; j<list.size(); j++) {
if(list.get(i).equals(list.get(j))) {
list.get(i).myEnum = MyEnum.TWORETURNS;
list.remove(j);
break;
}
}

}

在MyDTO中重写'equals'方法或添加特定的比较。

Answer 3

List<MyDTO> first = firstReturnMyDTO();
List<MyDTO> second = secondReturnMyDTO();
List< MyDTO > myDTOList = new ArrayList<>(first);
Set<MyDTO> uniqueSet = new HashSet<>();  
//remove from myDTOList those who are not present in second
myDTOList.retainAll(second);
//remove from first those who are present in myDTOList
first.removeAll(myDTOList);
//remove from second those who are present in myDTOList
second.removeAll(myDTOList);
//get the unique values
first.addAll(second); 
//handle the duplicates - stored in myDTOList
//adding them to the set will remove the duplicates. 
//Then, mark them with enum 3
uniqueSet.addAll(myDTOList);
for (MyDTO m : uniqueSet)
m.myEnum = MyEnum.TWORETURNS
//add the uniques to the set
uniqueSet.addAll(first);
//if wanted, convert to list
List<MyDTO> nonDuplicateList = new ArrayList<>(uniqueSet);

现在nonDuplicateList只包含不重复的条目。