java - 我需要帮助才能正确实现 Comparable 接口(interface)

Question

我构建了一个名为 Melody 的类，它从文件中读取以下几行并将它们存储到名为 Note 类型的音符的数组中。这些列是:以 1/100 秒为单位的时间、音符编号、速度、长度。

0 60 100 24
25 72 100 24
100 60 100 24
50 60 100 24
75 72 100 24

对于我的类(class)作业，我需要实现 Comparable 接口(interface)。我需要使我的 Note 类可比较，以便笔记根据时间排序，如果两个笔记同时出现，那么我需要将笔记编号较小的笔记放在前面。我需要一些帮助，因为我在尝试正确实现 comparaTo 方法并打印结果时遇到了困难。我将不胜感激任何帮助，提前致谢。

这是我的 Note 类

public class Note implements Comparable <Note> {  

    private int time;
    private int noteNumber;
    private int velocity;
    private int length;

    public Note (int time,int noteNumber,int velocity,int lenght){

        this.time = time;
        this.noteNumber = noteNumber;
        this.velocity = velocity;
        this.length = lenght;  
    }

    public String toString()
    {

        String s =  time +" "+ noteNumber + " " + velocity + " " + length;

        return s;   
    } 

    @Override
    public int compareTo(Note o) {

        return Integer.compare(time, o.time);
    }
} 

这是我的旋律课

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.StringTokenizer;

public class Melody  {

    Note [] notes = new Note[5];

    public Melody() throws IOException{

        FileReader fr = new FileReader ("/Users/enricomomo/Desktop/Text/file2.txt");
        BufferedReader br = new BufferedReader (fr); //Info stored into a buffer

        String line = br.readLine(); //Lines are read from the buffer and stored into a variable

        int lineCounter = 0;

        while  ( line != null )//When reached the end of the file the while loop stops 

        { 

            StringTokenizer st = new StringTokenizer(line, " ");

            int time = Integer.parseInt(st.nextToken());
            int noteNumber = Integer.parseInt(st.nextToken());
            int velocity = Integer.parseInt(st.nextToken());
            int length = Integer.parseInt(st.nextToken());

            System.out.println(line + " " + lineCounter);

            Note n = new Note(time,noteNumber,velocity,length);

            notes[lineCounter] = n;

            line = br.readLine();

            lineCounter ++;
        }

        br.close(); 
    }

    public void contet(){

        for ( int i = 0; i < notes.length; i ++)
        {

            System.out.println(notes[i]);                    
        }
    }

    public String toString()
    {
         String rtn = "";

         //Code to create a String version of the object 

         for ( int i = 0; i < notes.length; i ++)
            {

                rtn += "\n"; 
            }

         return rtn; 
    }
}    

这是我的测试课

import java.io.IOException;

public class Test {

    public static void main(String[] args) throws IOException {

        Melody m = new Melody();

        System.out.print(m);

        m.contet();
    } 
}

Answer 1

由于 time 和 noteNumber 是 int:

@Override
public int compareTo(Note o) {
    if (time == o.time)
        return Integer.compare(noteNumber, o.noteNumber);
    else
        return Integer.compare(time, o.time);
}

compareTo 需要返回负数、零或正数，
取决于第一项是小于、等于还是大于第二项。
填充 Note 对象数组后，调用:

Arrays.sort(notes);