Java - 按文件中的字符串属性对 ArrayList 进行排序 [英] Java - Sorting ArrayList by string attribute from file

问题描述

这就是我一整天都在努力实现的目标.我目前有一个类，它具有我的对象的属性，带有 setter 和 getter.我有另一个类，我在其中读取我的 CSV 文件并将其放入 ArrayList 中.文件的每一行都是一个对象，每一列都是我分配的属性，这在我执行 System.out.println 时有效.

Here is what I have been trying to achieve the whole day. I currently have a class which has the attributes for my objects with setters and getters. I have another class where I read my CSV file and put it in a ArrayList. Every row of the file is a object and every column is a attribute which I have assigned and this works when I do a System.out.println.

我现在想要的是创建一个类，该类可以按字符串属性对对象进行排序.我一整天都在尝试使用比较器，但我不知道自己在做什么.

What I now want to is create a class that can sort the objects by an attribute which is a string. How do I go about to do this as I have been trying all day using Comparators but I have no idea what I am doing.

推荐答案

假设您有一个这样的 CSV 文件:

Lets say you have a CSV file like this:

John,Smith,28
Jane,Doe,37

等等，那么我们就有了一个class Person，比如:

Etc, then we have a class Person, something like:

public class Person {
    private String firstName;
    private String lastName;
    private int age;

    //getters and setters

   //equals and hashCode
}

然后我们将文件逐行读入List.我们现在要按 lastName 对 List 进行排序.可以这样做:

We then read the file, line by line, into a List<Person>. We now want to sort the List by lastName. This can be done like so:

final List<Person> people = readFile();
people.sort(Comparator.comparing(Person::getLastName));

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