在Java中将层次列表转换为平面列表

Question

我有一个list下面的层次结构，我想将其转换为平面list。

我已经写了一种方法convertToFlatList并使用了它。但是最终结果中缺少一些要素。我做错什么了？

还有比我以前将列表转换为平面列表更好的方法吗？

我添加了一个示例代码和类似于我在场景中必须使用的对象的内容。最终结果应为1、2、3、4、5、6、7

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main
{
  public static void main(String[] args)
  {
    Member memberOne = new Member(1);
    Member memberTwo = new Member(2);
    Member memberThree = new Member(3);
    Member memberFour = new Member(4);
    Member memberFive = new Member(5);
    Member memberSix = new Member(6);
    Member memberSeven = new Member(7);

    memberTwo.setChildren(Arrays.asList(memberThree, memberFour));
    memberFour.setChildren(Arrays.asList(memberFive, memberSix));

    List<Member> memberList = Arrays.asList(memberOne, memberTwo, memberSeven);
    List<Member> flatList = new ArrayList<>();
    List<Member> convertedList = convertToFlatList(memberList, flatList);
    System.out.println(convertedList);
  }

  private static List<Member> convertToFlatList(List<Member> memberList, List<Member> flatList)
  {
    for (Member member : memberList)
    {
      if (member.getChildren() != null)
      {
        convertToFlatList(member.getChildren(), flatList);
      }
      else
      {
        flatList.add(member);
      }
    }
    return flatList;
  }
}

class Member
{
  private List<Member> children;

  private int memberId;

  Member(int memberId)
  {
    this.memberId = memberId;
  }

  List<Member> getChildren()
  {
    return children;
  }

  void setChildren(List<Member> children)
  {
    this.children = children;
  }

  int getMemberId()
  {
    return memberId;
  }

  void setMemberId(int memberId)
  {
    this.memberId = memberId;
  }

  @Override
  public String toString()
  {
    return String.valueOf(this.memberId);
  }
}

Answer 1

如果a
Member有子项，则可以正确地将子项添加到拼合列表中，但是会错过其Member本身。只需将成员的else添加移动到块添加之外，就可以了：

private static List<Member> 
convertToFlatList(List<Member> memberList, List<Member> flatList)
{
    for (Member member : memberList)
    {
        // Always add the member to flatList
        flatList.add(memeber);

        // If it has children, add them toore
        if (member.getChildren() != null)
        {
            convertToFlatList(member.getChildren(), flatList);
        }
    }
    return flatList;
}