HeadFirst Beatbox Sharpen your pencil

[Glen Roberts]

I've lurked around a long time and was trying to figure out something in the HeadFirst Java book and thought I'd ask for some input. If you're following along in the book Java HeadFirst page 464 wants you to use JFileChooser to save your beatbox "checkboxes". I'm just a little confused and was wondering if someone could explain/walk me through this.

My code is as follows

import java.awt.*;
import javax.swing.*;
import javax.sound.midi.*;
import java.io.*;
import java.util.*;
import java.awt.event.*;


public class BeatBox {

    JPanel mainPanel;
    ArrayList<JCheckBox> checkboxList;
    Sequencer sequencer;
    Sequence sequence;
    Track track;
    JFrame theFrame;

    String [] instrumentNames = {"Bass Drum", "Closed Hi-Hat",
            "Open Hi-Hat", "Acoustic Snare", "Crash Cymbal", "Hand Clap",
            "High Tom", "Hi Bongo", "Maracas", "Whistle", "Low Conga",
            "Cowbell", "Vibraslap", "Low-mid Tom", "High Agogo",
            "Open Hi Conga"};
    int[] instruments = {35,42,46,38,49,39,50,60,70,72,64,56,58,47,67,63};


    public static void main(String[] args) {
        new BeatBox().buildGUI();
    }

    public void buildGUI() {
        theFrame = new JFrame("Cyber BeatBox");
        theFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        BorderLayout layout = new BorderLayout();
        JPanel background = new JPanel(layout);
        background.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));

        checkboxList = new ArrayList<JCheckBox>();
        Box buttonBox = new Box(BoxLayout.Y_AXIS);

        JButton start = new JButton("Start");
        start.addActionListener(new MyStartListener());
        buttonBox.add(start);

        JButton stop = new JButton("Stop");
        stop.addActionListener(new MyStopListener());
        buttonBox.add(stop);

        JButton upTempo = new JButton("Tempo Up");
        upTempo.addActionListener(new MyUpTempoListener());
        buttonBox.add(upTempo);

        JButton downTempo = new JButton("Tempo Down");
        downTempo.addActionListener(new MyDownTempoListener());
        buttonBox.add(downTempo);

        JButton clear = new JButton("Clear Boxes");
        clear.addActionListener(new clearListener());
        buttonBox.add(clear);

        JButton serializeIt = new JButton("Serialize It");
        serializeIt.addActionListener(new MySendListener());
        buttonBox.add(serializeIt);

        JButton restoreIt =  new JButton("Restore");
        restoreIt.addActionListener(new MyReadListener());
        buttonBox.add(restoreIt);

        JButton saveIt = new JButton("Save It");
        saveIt.addActionListener(new SaveMenuListener());
        buttonBox.add(saveIt);

        Box nameBox = new Box(BoxLayout.Y_AXIS);
        for (int i = 0; i < 16; i++) {
            nameBox.add(new Label(instrumentNames[i]));
        }//close loop

        background.add(BorderLayout.EAST, buttonBox);
        background.add(BorderLayout.WEST, nameBox);

        theFrame.getContentPane().add(background);

        GridLayout grid = new GridLayout(16,16);
        grid.setVgap(1);
        grid.setHgap(2);
        mainPanel = new JPanel(grid);
        background.add(BorderLayout.CENTER, mainPanel);

        for (int i = 0; i < 256; i++) {
            JCheckBox c = new JCheckBox();
            c.setSelected(false);
            checkboxList.add(c);
            mainPanel.add(c);
        }//end loop

        setUpMidi();

        theFrame.setBounds(50,50,300,300);
        theFrame.pack();
        theFrame.setVisible(true);
    }//close buildGUI

    public void setUpMidi() {
        try {
            sequencer = MidiSystem.getSequencer();
            sequencer.open();
            sequence = new Sequence(Sequence.PPQ,4);
            track = sequence.createTrack();
            sequencer.setTempoInBPM(120);

        }catch(Exception e) {e.printStackTrace();}
    }//close setupmidi

    public void buildTrackAndStart() {
        int[] trackList = null;

        sequence.deleteTrack(track);
        track = sequence.createTrack();

        for (int i = 0; i < 16; i++) {
            trackList= new int[16];
            int key = instruments[i];
            for (int j = 0; j<16; j++) {
                JCheckBox jc = (JCheckBox) checkboxList.get(j + (16*i));
                if (jc.isSelected()) {
                    trackList[j] = key;
                } else {
                    trackList[j] = 0;
                }//close if
            }//close inner for loop

            makeTracks(trackList);
            track.add(makeEvent(176,1,127,0,16));
        }//close outer for loop

        track.add(makeEvent(192,9,1,0,15));
        try {
            sequencer.setSequence(sequence);
            sequencer.setLoopCount(sequencer.LOOP_CONTINUOUSLY);
            sequencer.start();
            sequencer.setTempoInBPM(120);
        }catch(Exception e) {e.printStackTrace();}
    }//close buildtrackandstart void

    public class MyStartListener implements ActionListener {
        public void actionPerformed(ActionEvent a) {
            buildTrackAndStart();
        }//close void
    }//close inner class

    public class MyStopListener implements ActionListener {
        public void actionPerformed(ActionEvent a) {
            sequencer.stop();
        }//close void
    }//close inner class

    public class MyUpTempoListener implements ActionListener {
        public void actionPerformed(ActionEvent a) {
            float tempoFactor = sequencer.getTempoFactor();
            sequencer.setTempoFactor((float) (tempoFactor * 1.03));
        }//close void
    }//close inner class

    public class MyDownTempoListener implements ActionListener {
        public void actionPerformed(ActionEvent a) {
            float tempoFactor = sequencer.getTempoFactor();
            sequencer.setTempoFactor((float)(tempoFactor * .97));
        }//close void
    }//close inner class

    public class clearListener implements ActionListener {
        public void actionPerformed(ActionEvent a) {
        //TODO Clear Check Boxes
            boolean[] checkboxState = null;
            for (int i = 0; i < 256;i++) {
                JCheckBox check = (JCheckBox) checkboxList.get(i);
                check.setSelected(false);
                sequencer.stop();
            }
        }//close void
    }//close inner class


    public void makeTracks(int[] list) {
        for (int i = 0; i<16; i++) {
            int key = list[i];

            if (key != 0) {
                track.add(makeEvent(144,9,key, 100, i));
                track.add(makeEvent(128,9,key, 100, i+1));
            }//close if
        }//close for loop
    }//close void

    public MidiEvent makeEvent(int comd, int chan, int one, int two, int tick) {
        MidiEvent event = null;
        try {
            ShortMessage a = new ShortMessage();
            a.setMessage(comd, chan, one, two);
            event = new MidiEvent(a, tick);

        }catch(Exception e) {e.printStackTrace();}
        return event;
    }//close midievent

    public class MySendListener implements ActionListener {
        public void actionPerformed(ActionEvent a) {
            boolean[] checkboxState = new boolean[256];

            for(int i = 0;i < 256;i++) {
                JCheckBox check = (JCheckBox) checkboxList.get(i);
                if(check.isSelected()) {
                    checkboxState[i] = true;
                }
            }
            try {
                FileOutputStream fileStream = new FileOutputStream(new File("Checkbox.ser"));
                ObjectOutputStream os = new ObjectOutputStream(fileStream);
                os.writeObject(checkboxState);
            } catch (Exception ex) {
                ex.printStackTrace();
            }
        }
    }//close MySendListener

    public class MyReadListener implements ActionListener {
        public void actionPerformed(ActionEvent a) {
            boolean[] checkboxState = null;
            try {
                FileInputStream fileIn = new FileInputStream(new File("Checkbox.ser"));
                ObjectInputStream is = new ObjectInputStream(fileIn);
                checkboxState = (boolean[]) is.readObject();
            } catch (Exception ex) {
                ex.printStackTrace();
            }

            for (int i = 0; i < 256;i++) {
                JCheckBox check = (JCheckBox) checkboxList.get(i);
                if(checkboxState[i]) {
                    check.setSelected(true);
                } else {
                    check.setSelected(false);
                }
            }
            sequencer.stop();
            //buildTrackAndStart(); disabled as I want to hit Play to start the song
        }
    } //close MyReadListener

    public class SaveMenuListener implements ActionListener {
        public void actionPerformed(ActionEvent ev) {


            JFileChooser fileSave = new JFileChooser();
            fileSave.showSaveDialog(theFrame);
            saveFile(fileSave.getSelectedFile());
        }
    }

    private void saveFile (File file) {
        try {
            BufferedWriter writer = new BufferedWriter(new FileWriter(file));
            //TODO Get the checkBoxState data and write it to file. At moment file is 0 bytes.
        } catch (IOException ex) {
            System.out.println("Couldn't write the selected file out");
            ex.printStackTrace();
        }
    }

}//close big class

So I understand that there isn't anything being written. When I put the following code it won't allow me to write the boolean array. I feel like I should know what to do but drawing a blank. This isn't for an assignment just me learning so if you could walk me through it I'd greatly appreciate it. Just didn't want someone to post "use this code" and I still feel lost.

            
            boolean[] checkboxState = new boolean[256];

            for(int i = 0;i < 256;i++) {
                JCheckBox check = (JCheckBox) checkboxList.get(i);
                if(check.isSelected()) {
                    checkboxState[i] = true;
                } else {
                   checkboxState[i] = false;
                }
            writer.write(checkboxState);
            writer.close();
            }

Thanks Again

[Campbell Ritchie]

Welcome to the Ranch

The file chooser doesn't save your file. What it does is allow you to find your file. Once the file is found you will have to write to it. You can read about file choosers in the Java® Tutorials. You appear to have a writing method in the second bit of code. Some style which needs improving however. You should change anything which looks like this:-

if (someMethodReturningBoolean())
{
   result = true;
}
else
{
   result = false;
}

to this:-

result = someMethodReturningBoolean();

What happens when you print a boolean[]? I know you can't simply write

System.out.println(myBooleanArray);

Well, you can, but since arrays never override toString, you won't get a helpful output. You can try

System.out.println(Arrays.toString(myArray));

… and you can read about that method here. That will probably print

[true,false,false,true,...true] or similar.

In your line 10 you are using a “writer”. Is that a BufferedWriter? If so, remember that a BufferedWriter writes text. So if you get it to work your file will contain similar text to what I showed you earlier.

Alternative: Iterate the array and use the ?: operator to tell the writer what to write

writer.write(myArray[i] ? "true" : "false");
writer.newLine(); // You get 256-line output file rather than 1-line like that.

You might do well to find out about Scanner and Formatter for reading and writing. You can use the %b and %n tags wtih Formatter for the output. You will have to work out what delimiter to use for a Scanner, but for the 256‑line version the default delimiter will probably do nicely. You can use the nextXXX methods of the Scanner to get different kinds of data from a text file.

If you have an array of check boxes, you don't need a boolean[]. You can simply iterate the box array and use its isSelected() method or similar to get the boolean, and you don't need the second array.

[Campbell Ritchie]

Something went wrong with the first version of my post and a line about Scanner/Formatter went missing. I have reposted it, with the missing bit restored, and deleted the original post.