存储在ArrayList中的。以及可比性接口是如何工作的？

Question

下面我粘贴了整个代码。

对于我们读取的DVDInfo.txt中的每一行文本，我们将创建DVDInfo类的新实例并将其存储在ArrayList中。到目前为止，请考虑这个类没有实现任何接口，在main方法中也没有使用任何排序方法。因此，在该条件下，当我们打印DVDListarraylist时，它会打印出文件中的所有内容，而不进行排序。我的第一个疑问是存储在ArrayList中的新实例如何正确地打印文本，我们没有使用任何getter方法来存储ArrayList中的文本。

现在考虑它在main中实现可比接口和collections.sort（）的整个代码。

The compareTo() method returns an int with the following characteristics:
* negative if thisObject < anotherObject 
* zero If thisObject == anotherObject 
* positive If thisObject > anotherObject 
    Wrote in SCJP by Kathy/Bates

Donnie Darko/sci-fi/Gyllenhall, Jake
Raiders of the Lost Ark/action/Ford, Harrison
2001/sci-fi/??
Caddy Shack/comedy/Murray, Bill
Star Wars/sci-fi/Ford, Harrison
Lost in Translation/comedy/Murray, Bill
Patriot Games/action/Ford, Harrison

import java.util.*;
import java.io.*;

class DVDInfo implements Comparable<DVDInfo>{
    String title;
    String genre;
    String leadActor;

    DVDInfo(String t, String g, String a){
        title = t; genre = g; leadActor = a;
    }

    public String toString(){
        return title + " " + genre + " " + leadActor + "\n";
    }

    public int compareTo(DVDInfo d){
        return title.compareTo(d.getTitle());
    }

    public String getTitle(){
        return title;
    }

    public String getGenre(){
        return genre;
    }

    public String getLeadActor(){
        return leadActor;
    }

    public void setTitle(String t){
        title = t;
    }

    public void setGenre(String g){
        genre = g;
    }
    public void setLeadActor(String l){
        leadActor = l;
    }


}

public class MyDVD{
    public static void main(String[] args){
        ArrayList<DVDInfo> dvdList = new ArrayList<DVDInfo>();
        populateList(dvdList);

        Collections.sort(dvdList);
        System.out.println(dvdList);

    }

    public static void populateList(ArrayList<DVDInfo> dvdList){
        try{    
            File file = new File("dvdinfo.txt"); 
            FileReader fr = new FileReader(file);
            BufferedReader br = new BufferedReader(fr);

            String s;
            while ((s = br.readLine()) != null){
                String[]tokens = s.split("/");
                dvdList.add(new DVDInfo(tokens[0],tokens[1],tokens[2]));
            }
            br.close();
        }catch(IOException e){System.out.println("File doesn\'t exist");}

    }

}

[2001 sci-fi ??
, Caddy Shack comedy Murray, Bill
, Donnie Darko sci-fi Gyllenhall, Jake
, Lost in Translation comedy Murray, Bill
, Patriot Games action Ford, Harrison
, Raiders of the Lost Ark action Ford, Harrison
, Star Wars sci-fi Ford, Harrison
]

Answer 1

印刷

它使用tostring()方法打印每个dvdinfo对象。

println方法将对其参数执行string.valueof()。然后println代码将打印结果字符串。