根据另一个列表中的条件删除一个列表中的某些元素 [英] Remove certain elements in one list based on condition from another list

问题描述

我是Java8的新手。我需要根据某些条件（来自另一个列表）在一个列表中减去/删除POJO并在UI上显示它。

I'm fairly new to Java8. I have a requirement to subtract/remove POJOs in one list based on certain criteria (from another list) and show it on UI.

迭代一个列表并搜索条件
删除对象
将原始列表发送到UI

Iterate one list and search for condition Remove the object Send the original list to UI

Children.java
private String firstName;
private String lastName;
private String school;
private String personId;
// Setters and getters.

Person.java
private String personId;
private String fullName;
private String address;
// Setters and Getters.

..主要代码..

  // populated by other methods.
  List<Person> personList;

 //Connect to DB and get ChildrenList
 List<Children> childrenList = criteria.list();

 for(Children child : childrenList) {
    personList.removeIf(person -> child.getPersonId().equals(person.getPersonId()));
 }

HANDLE for循环有没有更好的方法？感谢任何帮助。

Is there any BETTER way to HANDLE for-loop? Any help is appreciated.

推荐答案

您现在拥有的代码完美无缺，但也是 O （n * m）因为 removeIf 为每个<$ c $迭代 List C>儿童。改进的一种方法是将每个孩子的 personId 存储在 Set< String> 中并删除每个人来自列表< Person> ，如果他们的 personId 包含在设置：

The code that you have right now works perfectly, but is also O(n * m) since removeIf iterates through the List for every Children. One way to improve would be to store every child's personId in a Set<String> and remove every Person from the List<Person> if their personId is contained in the Set:

Set<String> childIds = childrenList.stream()
                                   .map(Children::getPersonId)
                                   .collect(Collectors.toSet());

personList.removeIf(person -> childIds.contains(person.getPersonId()));

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