Java クラスの紹介用にプロジェクトを作成する必要があり、最終的に構文エラーを整理した後、再生ボタンまたは保存ボタンをクリックすると、このプログラムで実行時エラーが発生します。
//C:\\Users\\Andrew\\Downloads\\never gonna give you up.wav
//Andrew Douglas
//Imports
import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.sound.sampled.*;
import javax.swing.filechooser.*;
import javax.swing.JTable;
//Creates class
public class JPlayer extends JFrame implements ActionListener {
//Sets up form items and necessary globals
JButton save, play, stop, loop;
JFileChooser dialog;
JTable table;
String Artist, Song, Album, Loc;
Object[][] data;
int n = 1;
//Makes the library, with a 51 song limit.
JLibrary[] addedSong = new JLibrary[50];
public JPlayer() {
super ("JPlayer");
//Creates frame
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setTitle("jPlayer");
this.setSize(800, 600);
//Makes titles for table
String[] columnNames = {"Artist",
"Song",
"Album",
"Location"};
//Gives one value for array
addedSong[0] = new JLibrary ("Rick Astley", "NGGYU", "UnKnown", "C:\\Users\\Andrew\\Downloads\\never gonna give you up.wav");
//Adds it to table array
Object[][] data = {
{
(addedSong[0].returnArtist()), (addedSong[0].returnSong()), (addedSong[0].returnAlbum()), (addedSong[0].returnFile())
}
};
//Creates table
JTable table = new JTable(data, columnNames);
table.setPreferredScrollableViewportSize(new Dimension(500, 70));
table.setFillsViewportHeight(true);
//Lets it sort the rows
table.setAutoCreateRowSorter(true);
//Creates the scroller
JScrollPane scrollPane = new JScrollPane(table);
//Makes the save file dialog and the play and save buttons
dialog = new JFileChooser();
play = new JButton ("Play Song");
save = new JButton ("Save a file");
//Adds the button listeners
save.addActionListener(this);
play.addActionListener(this);
//Adds buttons to panel
JPanel buttons = new JPanel();
buttons.add(save);
buttons.add(play);
//Puts the buttons at the bottom
add(buttons, BorderLayout.SOUTH);
add(scrollPane);
this.setVisible(true);
}
//Creates action listener for button
public void actionPerformed(ActionEvent e) {
if (e.getSource() == save) {
dialog.setFileFilter(new FileNameExtensionFilter("Wave File (*.wav)"));
int returnVal = dialog.showSaveDialog(JPlayer.this);
if (returnVal == dialog.APPROVE_OPTION) {
File file = dialog.getSelectedFile();
addToLibrary("", "", "", file.getName());
}
}
else if (e.getSource() == play) {
String holder2;
Object holder;
holder = table.getValueAt(table.getSelectedRow(), 3);
try {
File soundFile = new File(holder.toString());
AudioInputStream audioIn = AudioSystem.getAudioInputStream(soundFile);
Clip clip = AudioSystem.getClip();
clip.open(audioIn);
clip.start();
} catch (UnsupportedAudioFileException f) {
f.printStackTrace();
} catch (IOException f) {
f.printStackTrace();
} catch (LineUnavailableException f) {
f.printStackTrace();
}
} }
public static void main(String[]args) {
new JPlayer();
}
public void addToLibrary(String art, String song, String alb, String file) {
addedSong[n] = new JLibrary(art, song, alb, file);
int j = 0;
while (n >= 0) {
Object[][] data = {
{
addedSong[(n-j)],
}
};
j = j+1;
}
n = n +1;
}
}
再生ボタンをクリックしてファイル内の音楽の再生を開始するたびに、次のエラーが発生します。
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at JPlayer.actionPerformed(JPlayer.java:86)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:729)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:688)
at java.awt.EventQueue$3.run(EventQueue.java:686)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:702)
at java.awt.EventQueue$4.run(EventQueue.java:700)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:699)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
保存ボタンをクリックすると、次のエラーが表示されます。
Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: Extensions must be non-null and not empty
at javax.swing.filechooser.FileNameExtensionFilter.<init>(FileNameExtensionFilter.java:76)
at JPlayer.actionPerformed(JPlayer.java:75)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:729)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:688)
at java.awt.EventQueue$3.run(EventQueue.java:686)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:702)
at java.awt.EventQueue$4.run(EventQueue.java:700)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:699)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
何が問題なのか、それを修正する方法を教えてくれる人がいるでしょうか？どんな助けでも大歓迎です、私はこのことで少し遅いです:)