我有这个类 Playlist 和这个类 PlaylistOperations，我想在 PlaylistOperations 中实现一个来自 Playlist 的类 toString。每次我尝试在 PlaylistOperations 中使用 toString 时，我的程序都会崩溃。addSong 也会发生同样的事情。我真的需要能够以这种方式实现它，我尝试使用 Playlist.toString() 但是当我将 toString 方法设为静态时，它只是说让它非静态导致循环。
以下是播放列表操作
public class PlaylistOperations extends Playlist{
public static void main(String[] args) {
JFrame mainMenu = new JFrame("Main Menu");
JPanel mainPane = new JPanel();
mainMenu.add(mainPane);
mainMenu.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
mainPane.setLayout(new FlowLayout());
JButton addSong = new JButton("Add Song");
mainPane.add(addSong);
JButton printSongs = new JButton("Print Songs by Artist");
mainPane.add(printSongs);
JButton getSong = new JButton("Get Song");
mainPane.add(getSong);
JButton removeSong = new JButton("Remove Song");
mainPane.add(removeSong);
JButton printAllSongs = new JButton("Print All Songs");
mainPane.add(printAllSongs);
JButton size = new JButton("Size");
mainPane.add(size);
JButton quit = new JButton("Quit");
mainPane.add(quit);
mainMenu.pack();
mainMenu.setSize(800, 200);
mainMenu.setVisible(true);
mainPane.setVisible(true);
addSong.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
new Playlist().addSong();
}
});
printSongs.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
}
});
getSong.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
}
});
removeSong.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
}
});
printAllSongs.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
JFrame toStringFrame = new JFrame("Songs in Playlist");
toStringFrame.setVisible(true);
toStringFrame.pack();
toStringFrame.setSize(250,250);
JPanel toStringPanel = new JPanel();
toStringFrame.add(toStringPanel);
JLabel printed = new JLabel(one.toString());
toStringPanel.add(printed);
}
});
size.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int amountOfSongs = 0;
for (int x = 0; x < 50; x++) {
if (slotFull(new Playlist().songs, x)) {
amountOfSongs++;
}
}
final JFrame amountOfSongsFrame = new JFrame("Amount of songs");
JPanel amountOfSongsPanel = new JPanel();
JLabel amountOfSongsLabel = new JLabel("There are "
+ amountOfSongs + " songs in this playlist.");
JButton okayEnterText = new JButton("Okay");
amountOfSongsFrame.setVisible(true);
okayEnterText.setPreferredSize(new Dimension(100, 27));
amountOfSongsFrame.add(amountOfSongsPanel);
amountOfSongsPanel.add(amountOfSongsLabel);
amountOfSongsPanel.add(okayEnterText);
amountOfSongsFrame.pack();
amountOfSongsFrame.setSize(300, 200);
okayEnterText.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
amountOfSongsFrame.dispose();
}
});
}
});
quit.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
final JFrame exit = new JFrame(
"Are you sure you would like quit?");
JPanel exiter = new JPanel();
exit.add(exiter);
exit.setVisible(true);
JButton yes = new JButton("Yes");
exiter.add(yes);
JButton no = new JButton("No");
exiter.add(no);
exit.pack();
exit.setSize(450, 150);
exiter.setSize(450, 150);
yes.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
});
no.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
exit.dispose();
}
});
}
});
}
public static boolean slotFull(SongRecord[] songs, int x) {
boolean slotFull = true;
if (new Playlist().songs[x].getTitle() == "" && new Playlist().songs[x].getArtist() == ""
&& new Playlist().songs[x].getSongLengthMinutes() == 0
&& new Playlist().songs[x].getSongLengthSeconds() == 0) {
slotFull = false;
}
return slotFull;
}
}
这是播放列表
public class Playlist {
public Playlist() {
for (int x = 0; x < 50; x++) {
songs[x].setTitle("");
songs[x].setArtist("");
songs[x].setSongLengthMinutes(0);
songs[x].setSongLengthSeconds(0);
}
}
public Object clone() {
}
public boolean equals(Object obj) {
}
public int size() {
}
public void addSong() {
final JFrame newSong = new JFrame("New Song");
newSong.setVisible(true);
newSong.pack();
newSong.setSize(450, 230);
JPanel songSettings = new JPanel();
newSong.add(songSettings);
JLabel titleLabel = new JLabel("Enter the song title: ");
songSettings.add(titleLabel);
final JTextField titleEnter = new JTextField(20);
songSettings.add(titleEnter);
JLabel artistLabel = new JLabel("Enter the song artist: ");
songSettings.add(artistLabel);
final JTextField artistEnter = new JTextField(20);
songSettings.add(artistEnter);
JLabel minutesLabel = new JLabel(
"Enter the song length (minutes): ");
songSettings.add(minutesLabel);
final JTextField minutesEnter = new JTextField(20);
songSettings.add(minutesEnter);
JLabel secondsLabel = new JLabel(
"Enter the song length (seconds): ");
songSettings.add(secondsLabel);
final JTextField secondsEnter = new JTextField(20);
songSettings.add(secondsEnter);
JLabel positionLabel = new JLabel("Enter the position: ");
songSettings.add(positionLabel);
final JTextField positionEnter = new JTextField(20);
songSettings.add(positionEnter);
JButton enter = new JButton("Enter");
songSettings.add(enter);
enter.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (!positionEnter.getText().isEmpty()
&& !titleEnter.getText().isEmpty()
&& !artistEnter.getText().isEmpty()
&& !minutesEnter.getText().isEmpty()
&& !secondsEnter.getText().isEmpty()) {
String positionString = positionEnter.getText();
int position = Integer.parseInt(positionString);
String title = titleEnter.getText();
songs[position].setTitle(title);
String artist = artistEnter.getText();
songs[position].setArtist(artist);
String songLengthMinutesString = minutesEnter
.getText();
int songLengthMinutes = Integer
.parseInt(songLengthMinutesString);
songs[position].setSongLengthMinutes(songLengthMinutes);
String songLengthSecondsString = secondsEnter
.getText();
int songLengthSeconds = Integer
.parseInt(songLengthSecondsString);
songs[position].setSongLengthSeconds(songLengthSeconds);
newSong.dispose();
final JFrame songAdded = new JFrame("Song Added");
songAdded.setVisible(true);
songAdded.pack();
songAdded.setSize(250, 300);
JPanel songAddedPanel = new JPanel();
songAdded.add(songAddedPanel);
JLabel addedSongText = new JLabel(
"You have added the song " + title);
songAdded.add(addedSongText);
JButton okay = new JButton("Okay");
songAdded.add(okay);
okay.setPreferredSize(new Dimension(100, 27));
okay.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
songAdded.dispose();
}
});
} else {
final JFrame enterText = new JFrame(
"Please Enter Text");
JPanel enterTextPanel = new JPanel();
JLabel enterTextLabel = new JLabel(
"Please enter text in " + "all the fields.");
JButton okayEnterText = new JButton("Okay");
enterText.setVisible(true);
okayEnterText.setPreferredSize(new Dimension(100,
27));
enterText.add(enterTextPanel);
enterTextPanel.add(enterTextLabel);
enterTextPanel.add(okayEnterText);
enterText.pack();
enterText.setSize(300, 200);
okayEnterText
.addActionListener(new ActionListener() {
public void actionPerformed(
ActionEvent e) {
enterText.dispose();
}
});
}
}
});
JButton cancel = new JButton("Cancel");
songSettings.add(cancel);
enter.setPreferredSize(new Dimension(100, 27));
cancel.setPreferredSize(new Dimension(100, 27));
cancel.addActionListener (new ActionListener() {
public void actionPerformed(ActionEvent e) {
newSong.dispose();
}
{;
}
;
});
}
public void removeSong(int position) {
}
public SongRecord getSong(int position) {
}
public void printAllSongs() {
}
public static Playlist getSongsByArtist(Playlist originalList, String artist) {
}
public String toString() {
System.out.print("test");
String a ="Song#";
String b ="Title";
String c ="Artist";
String d ="Length";
String e ="------------------------------------------------";
String finalString = String.format("%-21s%-26s%19s%06d", a, b, c,
d)+ "\n"+e;
for(int x =0;x<50;x++){
if(PlaylistOperations.slotFull(songs, x)){
finalString+= "\n" + String.format("%-21s%-26s%19s%06d", x, new SongRecord().getTitle(), new SongRecord().getArtist(),
new SongRecord().getSongLengthMinutes() +":"+new SongRecord().getSongLengthSeconds());
}
}
return finalString;
}
final int arraySize = 50;
SongRecord[] songs = new SongRecord[arraySize];
}