将列表拆分为重复列表和非重复列表Java8

Question

我有一个可能包含或不包含重复值的列表：

如果有重复的“ ABC”值（此问题仅是ABC）

List myList = {“ ABC”，“ EFG”，“ IJK”，“ ABC”，“ ABC”}，

我想将列表分为两个列表以最终得到：

列出重复值= {“ ABC”};

列出nonDuplicatedValues = {“ EFG”，“ IJK”};

同样，如果列表中不止一个“ ABC”，它将返回相同的列表

我到目前为止所做的：

void generateList(List<String> duplicatedValues, List<String> nonDuplicatedValues){

    List<String> myList=List.of("ABC","EFG","IJK","ABC","ABC");
    Optional<String> duplicatedValue = myList.stream().filter(isDuplicated -> Collections.frequency(myList, "ABC") > 1).findFirst();

    if(duplicatedValue.isPresent())
    {
        duplicatedValues.addAll(List.of(duplicatedValue.get()));
        nonDuplicatedValues.addAll(myList.stream().filter(string->string.equals("ABC")).collect(Collectors.toList()));
    }
    else
    {
        nonDuplicatedValues.addAll(myList);
    }
}

是否存在仅使用myList流的更有效方法？

Answer 1

您可以两次播放列表，如下所示：

public static void main(String[] args) {
    // example list with values
    List<String> myList = new ArrayList<>();
    myList.add("ABC");
    myList.add("EFG");
    myList.add("IJK");
    myList.add("ABC");
    myList.add("ABC");

    // print the original list once
    System.out.println("Source List:     " + String.join(", ", myList));

    // stream the list 
    List<String> distinctValues = myList.stream()
                                        // and collect all the values that occur exactly once 
                                        .filter(i -> Collections.frequency(myList, i) == 1)
                                        .collect(Collectors.toList());

    // print the result
    System.out.println("Distinct Values: " + String.join(", ", distinctValues));

    // stream the list again
    List<String> duplicates = myList.stream()
                                    // and collect all the values that occur more than once
                                    .filter(i -> Collections.frequency(myList, i) > 1)
                                    // and don't allow duplicate entries
                                    .distinct()
                                    .collect(Collectors.toList());

    // then print the result
    System.out.println("Duplicates:      " + String.join(", ", duplicates));
}

此示例的输出是

Source List:     ABC, EFG, IJK, ABC, ABC
Distinct Values: EFG, IJK
Duplicates:      ABC