Question

这是问题的扩展。我有一个消息列表。我想创建一个包含审计值的自定义消息列表。

list of id from a list of age using java 8

public class Messages {

int id;
String message;
int audId;
String audmessage;

public int getId() {
    return id;
}

public void setId(int id) {
    this.id = id;
}

public String getMessage() {
    return message;
}

public void setMessage(String message) {
    this.message = message;
}

public int getAudId() {
    return audId;
}

public void setAudId(int audId) {
    this.audId = audId;
}

public String getAudmessage() {
    return audmessage;
}

public void setAudmessage(String audmessage) {
    this.audmessage = audmessage;
}

public Messages(int id, String message, int audId, String audmessage) {

    this.id = id;
    this.message = message;
    this.audId = audId;
    this.audmessage = audmessage;
  }
}


public class CustomMessage {

int id;
String msg;
List<Aud> list;
//getters and setters
 }

public class Aud {

int id;
int message;
   //getters and setters
 }


  public class Demo {

    public static  void main(String args[]){
      List<Messages> list = new ArrayList<Messages>();
      list.add(new Messages(1,"abc",10,"a1"));
      list.add(new Messages(2,"ac",21,"a2"));
      list.add(new Messages(3,"adc",31,"a3"));
      list.add(new Messages(4,"aec",40,"a4"));
      list.add(new Messages(1,"abc",11,"a5"));
      list.add(new Messages(2,"ac",22,"a5"));
     }

预期输出为1，abc-＆gt;审核清单为（10，a1），（11，a5）;

Answer 1

这里的答案（如果我理解正确的话）几乎与上一个问题中的答案相同，只有几个假设。首先，您的<Project> <Import Project="Sdk.props" Sdk="Microsoft.NET.Sdk" /> <PropertyGroup> <TargetFramework>net46</TargetFramework> </PropertyGroup> <Import Project="Sdk.targets" Sdk="Microsoft.NET.Sdk" />  <Target Name="BeforeBuild"> <Message Text="Should run before build" Importance="High" /> </Target> <Target Name="AfterBuild"> <Message Text="Should run after build" Importance="High" /> </Target> </Project>构造函数实际存在，如下所示：

Aud

而没有<{em> public Aud(int id, String message) { this.id = id; this.message = message; } Holder，因此我使用了id and message。

AbstractMap.SimpleEntry

修改

Map<SimpleEntry<Integer, String>, List<Aud>> map = list.stream() .collect(Collectors.groupingBy( m -> new SimpleEntry<>(m.getId(), m.getMessage()), Collectors.mapping( m -> new Aud(m.getAudId(), m.getAudMessage()), Collectors.toList())));

我不知道List<CustomMessage> l = list.stream() .collect(Collectors.groupingBy(m -> new SimpleEntry<>(m.getId(), m.getMessage()), Collectors.mapping(m -> new Aud(m.getAudId(), m.getAudMessage()), Collectors.toList()))) .entrySet() .stream() .map(e -> new CustomMessage(e.getKey().getKey(), e.getKey().getValue(), e.getValue())) .collect(Collectors.toList());应该是什么意思。

如果你使用的是setter和getter，你可以替换它：

want to check for null using optional

with：

m -> new Aud(m.getAudId(), m.getAudMessage())

java 8从对象列表

1 个答案: