java - 如何按字符串对象的升序对对象数组进行排序？

Question

我必须接受用户输入(int id、字符串标题、字符串文件夹、int 页面)。我必须按字符串标题(字典)的升序排列输出。我已经编写了代码，但输出却截然不同。

package zzz;
import java.util.Scanner;
import java.util.Arrays;
import java.util.Collections;

class Book{
    int id;
    String title;
    String folder;
    int pages;
}


public class practice {

    public static void main(String[] args)throws Exception {
        // TODO Auto-generated method stub
    Scanner sc = new Scanner(System.in);
    Book b1 = new Book();
    Book b2 = new Book();
    Book b3 = new Book();
    Book b[]= {b1,b2,b3};
    for(int i=0;i<b.length;i++) {
        b[i].id=sc.nextInt();
        sc.nextLine();
    b[i].title=sc.next();
        sc.nextLine();
        b[i].folder=sc.next();
        b[i].pages=sc.nextInt();
    }
    Book temp = null;
    for(int i=0;i<b.length;i++) {
        for(int j=0;j<b.length-1-i;j++) {
            if(b[i].title.compareTo(b[j].title)<0) {
             temp =b[j];
            b[j]=b[j+1];
            b[j+1]=temp;
        }}
    }
    for(int i=0;i<b.length;i++) {
        System.out.println(b[i].id+" "+b[i].title+" "+b[i].folder+" "+b[i].pages);
    }

    }}

Answer 1

我会删除开头的类并在 main 方法之后添加该类，如下所示:

static class Book implements Comparable<Book>{
    int id;
    String title;
    String folder;
    int pages;

    @Override
    public int compareTo(Book other) {
        //If this is backword then switch it to -> other.title.compareTo(this.title);
        return this.title.compareTo(other.title);
     }
}

与:Implements Comparable to get alphabetical sort with Strings相同

然后你可以获取书籍数组并使用Arrays.sort(book_arr);

给你:

package zzz;
import java.util.Scanner;
import java.util.Arrays;
import java.util.Collections;


public class practice {

    public static void main(String[] args)throws Exception {
        // TODO Auto-generated method stub
    Scanner sc = new Scanner(System.in);
    Book b1 = new Book();
    Book b2 = new Book();
    Book b3 = new Book();
    Book b[]= {b1,b2,b3};
    for(int i=0;i<b.length;i++) {
        b[i].id=sc.nextInt();
        sc.nextLine();
        b[i].title=sc.next();
        sc.nextLine();
        b[i].folder=sc.next();
        b[i].pages=sc.nextInt();
    }

    //Sort!
    Arrays.sort(b);

    for(int i=0;i<b.length;i++) {
        System.out.println(b[i].id+" "+b[i].title+" "+b[i].folder+" "+b[i].pages);
    }

    }
    static class Book implements Comparable<Book>{
        int id;
        String title;
        String folder;
        int pages;

        @Override
         public int compareTo(Book other) {
             return this.title.compareTo(other.title);
         }
     }
}