改变code使其实现同样的功能

[zrmzhang]

main.java

public class Main {

	public static void main(String[] args) {

		// init
		Track track11 = new Track("track 11", "artist 1", 3.45);
		Track track12 = new Track("track 12", "artist 1", 3.44);
		Track track13 = new Track("track 13", "artist 1", 3.43);
		Track track14 = new Track("track 14", "artist 1", 3.42);
		Track track15 = new Track("track 15", "artist 1", 3.41);

		Track track21 = new Track("track 21", "artist 2", 3.59);
		Track track22 = new Track("track 22", "artist 2", 2.44);
		Track track23 = new Track("track 23", "artist 2", 3.12);
		Track track24 = new Track("track 24", "artist 2", 4.47);
		Track track25 = new Track("track 25", "artist 2", 8.25);
		
		Track track31 = new Track("track 31", "artist 31", 3.47);
		Track track32 = new Track("track 32", "artist 32", 5.75);
		Track track33 = new Track("track 33", "artist 33", 8.26);
		Track track34 = new Track("track 34", "artist 34", 2.45);
		Track track35 = new Track("track 35", "artist 35", 1.42);
		
		Disc disc1 = new Disc("album 1", "artist 1");
		Disc disc2 = new Disc("album 2", "artist 2");
		Disc disc3 = new Disc("album 3", "various artists");
		
		Player player = new Player();
		
		// add tracks to discs
		disc1.addTrack(track11);
		disc1.addTrack(track12);
		disc1.addTrack(track13);
		disc1.addTrack(track14);
		disc1.addTrack(track15);
		
		disc2.addTrack(track21);
		disc2.addTrack(track22);
		disc2.addTrack(track23);
		disc2.addTrack(track24);
		disc2.addTrack(track25);
		
		disc3.addTrack(track31);
		disc3.addTrack(track32);
		disc3.addTrack(track33);
		disc3.addTrack(track34);
		disc3.addTrack(track35);
		
		// add discs to player
		player.addDisc(disc1);
		player.addDisc(disc2);
		player.addDisc(disc3);
		
		// remove disc1 (which is the current disc)
		player.removeDisc();
		
		// play track 4 of disc3 
		player.nextDisc();
		player.nextTrack();
		player.nextTrack();
		player.nextTrack();
		player.play();
		
		// display current disc and track info
		System.out.println("Current disc playing time " + player.getDiscPlayingTime());
		System.out.println("Current track playing length " + player.getTrackLength());
		
		// stop playing 
		player.stop();
		
	}
}

import java.util.ArrayList;

Disc.java

public class Disc {
	
	private String title;
	private String artist;
	private int currentTrack;
	private ArrayList<Track> tracks;

	public Disc(String title, String artist) {
		this.title = title;
		this.artist = artist;
		tracks = new ArrayList<Track>();
	}

	public void addTrack(Track track) {
		tracks.add(track);
	}

	public void play() {
		tracks.get(currentTrack).play();
	}

	public void stop() {
		currentTrack = 0;
	}

	public void nextTrack() {
		currentTrack++;
		if (currentTrack == tracks.size()) {
			currentTrack = 0;
		}
	}

	public double getDiscPlayingTime() {
		double playingTime = 0.0;
		for (Track track : tracks) {
			playingTime += track.getTrackLength();
		}
		return playingTime;
	}

	public double getTrackLength() {
		return tracks.get(currentTrack).getTrackLength();
	}
}

Player.java

public class Player {
	
	private int currentDisc;
	private ArrayList<Disc> discs;

	public Player() {
		discs = new ArrayList<Disc>();
	}

	public void addDisc(Disc disc) {
		discs.add(disc);
	}

	public void removeDisc() {
		discs.remove(currentDisc);
	}

	public void nextDisc() {
		currentDisc++;
		if (currentDisc == discs.size()) {
			currentDisc = 0;
		}
	}

	public void nextTrack() {
		discs.get(currentDisc).nextTrack();
	}

	public void play() {
		discs.get(currentDisc).play();
	}

	public void stop() {
		discs.get(currentDisc).stop();
	}

	public double getDiscPlayingTime() {
		return discs.get(currentDisc).getDiscPlayingTime();
	}

	public double getTrackLength() {
		return discs.get(currentDisc).getTrackLength();
	}

Track.java

public class Track {
	private String title;
	private String artist;
	private double length;

	public Track(String title, String artist, double length) {
		this.title = title;
		this.artist = artist;
		this.length = length;
	}

	public double getTrackLength() {
		return length;
	}

	public void play() {
		System.out.println("Now playing... " + artist + " " + title);
	}
}

[古布]

LZ代码挺整，要改的话，也就是main 方法优化一下。数据可以采取读文件或者DB的方式。