java - 从 Java 中的另一个 ArrayList 获取 ArrayList 的 ArrayList

Question

我有一个 MyClass 的 ArrayList，我需要根据类的属性的重复从中提取多个列表。

我的类(class):

public class MyClass{
    private int ID;
    private String Name;
    private String Position;

    public MyClass(int ID, String name, String position){
        this.ID = ID;
        Name = name;
        Position = position;
    }
}

例子:

在我的 ArrayList 中，我有 5 个对象:

ID = 0, Name = "Name 0", Position = "G1.1";
ID = 1, Name = "Name 1", Position = "G2.1";
ID = 2, Name = "Name 2", Position = "G1.1";
ID = 3, Name = "Name 3", Position = "G1.1";
ID = 4, Name = "Name 4", Position = "G2.1";

我将从这个列表中创建 2 个 ArrayList:

ArrayList 1 (Where Position = "G1.1")
    ID = 0, Name = "Name 0", Position = "G1.1";
    ID = 2, Name = "Name 2", Position = "G1.1";
    ID = 3, Name = "Name 3", Position = "G1.1";
ArrayList 2 (Where Position = "G2.1")
    ID = 1, Name = "Name 1", Position = "G2.1";
    ID = 4, Name = "Name 4", Position = "G2.1";

主列表是动态创建的，所以我不知道我需要创建什么位置来获取项目。

Answer 1

您可以像这样将项目一起收集到 map 中:

Map<String, List<MyClass>> grp = l.stream().collect(Collectors.groupingBy(o -> o.Position));