August 6, 2015

Head First Java: Midi and Swing

Now that I found a job where I get paid to write code, I might as well try to practice the language, eh?

Over the past few months, in my quest to practice being a developer, I have been trying to come up with cute little side-projects in Java that I could do in my free time, and I have been reading more than a few textbooks to come up with ideas.

I first heard of "Head First Java (2nd Edition, 2005)" back in February when I was interviewing for automated testing positions over at Harvard University. Although I didn't get the position, when the hiring manager and I exchanged emails afterwards he referred me to two books to help me brush up on my Java skills, long unused as a manual software tester. I was referred to: Murach's Java Programming ( Official Site)  and Head First Java ( Official Site ). After reading a few sample chapters of each book, I went with "Head First Java".

Head First Java

 I have to say, I have never been so amused by a computer programming textbook! Thank you, Gray, for referring me to it! It talks about how Java manages memory, about creating multi-threading apps, sockets, user interfaces with Java's Swing library, and making music through Java's MIDI library but it does it in such a hilarious way that it cracks you up, with stock images from the 1950s, jokes, bad puns, and mock interviews with the concepts they are talking about.

As found on

What caught my eye were the following blurbs in the introduction:

"Who the book is for: 
"Do you prefer stimulating dinner party conversation to dry, dull, academic lectures?" Head First Java: Intro Who the book is not for: "Are you afraid to try something different? Would you rather have a root canal than mix stripes with plaid? Do you believe than a technical book can't be serious if there's a picture of a duck in the memory management section?" - Head First Java: Intro
"Who the book is not for: 
"Are you afraid to try something different? Would you rather have a root canal than mix stripes with plaid? Do you believe than a technical book can't be serious if there's a picture of a duck in the memory management section?" Head First Java: Intro
It's quite a funny book! After spending so much time with very dry texts studying, I found it to be a refreshing change of pace to get me back in the swing of things re-learning Java.

Warning: They have a lot of cute graphics, like the ones above.

My Favorite Project: The BeatBox app

My favorite code example of theirs was the BeatBox application found in their chapter on Using Swing, Java's built-in graphical user interface toolset. I remember getting into developing user interfaces as a Computer Science major, using Charles Petzold's textbook Programming Windows using C and Windows 95. When I encountered the Java's Swing library in my Advanced Programming in Java class in grad school, I found it a lot easier to work with.

With the BeatBox app, they combine the Swing Library with Musical Instrument Digital Interface (MIDI) library as part of Java's Sound API.

My version of the BeatBox app

Sidenote: The Java Sound API:

"The Java Sound API is a low-level API for effecting and controlling the input and output of sound media, including both audio and Musical Instrument Digital Interface (MIDI) data. The Java Sound API provides explicit control over the capabilities normally required for sound input and output, in a framework that promotes extensibility and flexibility. 
"The Java Sound API fulfills the needs of a wide range of application developers. Potential application areas include:
  • "Communication frameworks, such as conferencing and telephony
  • "End-user content delivery systems, such as media players and music using streamed content
  • "Interactive application programs, such as games and Web sites that use dynamic content
  • "Content creation and editing
  • "Tools, toolkits, and utilities
"The Java Sound API provides the lowest level of sound support on the Java platform. It provides application programs with a great amount of control over sound operations, and it is extensible. For example, the Java Sound API supplies mechanisms for installing, accessing, and manipulating system resources such as audio mixers, MIDI synthesizers, other audio or MIDI devices, file readers and writers, and sound format converters. The Java Sound API does not include sophisticated sound editors or graphical tools, but it provides capabilities upon which such programs can be built. It emphasizes low-level control beyond that commonly expected by the end user. - The Java Tutorials: Sound

Sidenote: About MIDI:

"MIDI was originally designed for passing musical events, such as key depressions, between electronic keyboard instruments such as synthesizers. Hardware devices known as sequencers stored sequences of notes that could control a synthesizer, allowing musical performances to be recorded and subsequently played back. Later, hardware interfaces were developed that connected MIDI instruments to a computer's serial port, allowing sequencers to be implemented in software. More recently, computer sound cards have incorporated hardware for MIDI I/O and for synthesizing musical sound. Today, many users of MIDI deal only with sound cards, never connecting to external MIDI devices. CPUs have become fast enough that synthesizers, too, can be implemented in software. A sound card is needed only for audio I/O and, in some applications, for communicating with external MIDI devices. - The Java Tutorials: The MIDI Package
With the chapter in Head First Java: Using Swing, they walk you through:

  • Setting up a list of sixteen percussion instruments, taken from the MIDI Percussion Key Map. 
  • Set up a Sequencer to play the music, playing the sequence chosen by the user. It's a fast tempo, 120 beats per minute. The tempo can raised or lowered by the user. 
  • Set up a GUI with a list of the 16 percussion instruments the user can choose from in the far right column. By checking one of sixteen checkboxes for that instrument, the user crafts the sequence that will be played in a continuous loop. 
  • Listeners are placed on a Start and a Stop button to play and pause the beatbox. 

Even though you can download the sourcecode from the book, cutting and pasting what you need, I find it is easier for me to understand the code by manually typing the code out and experimenting with it. 

A Few Modifications:

I made a few changes with the program:

Adding New Instrument:

There are a lot more percussion instruments than the sixteen shown in the example.

General MIDI Level 1 Percussion Key Map
On MIDI Channel 10, each MIDI Note number ("Key#") corresponds to a different drum sound, as shown below. GM-compatible instruments must have the sounds on the keys shown here. While many current instruments also have additional sounds above or below the range show here, and may even have additional "kits" with variations of these sounds, only these sounds are supported by General MIDI Level 1 devices.
Key#Drum SoundKey#Drum Sound
35Acoustic Bass Drum59Ride Cymbal 2
36Bass Drum 160Hi Bongo
37Side Stick61Low Bongo
38Acoustic Snare62Mute Hi Conga
39Hand Clap63Open Hi Conga
40Electric Snare64Low Conga
41Low Floor Tom65High Timbale
42Closed Hi Hat66Low Timbale
43High Floor Tom67High Agogo
44Pedal Hi-Hat68Low Agogo
45Low Tom69Cabasa
46Open Hi-Hat70Maracas
47Low-Mid Tom71Short Whistle
48Hi-Mid Tom72Long Whistle
49Crash Cymbal 173Short Guiro
50High Tom74Long Guiro
51Ride Cymbal 175Claves
52Chinese Cymbal76Hi Wood Block
53Ride Bell77Low Wood Block
54Tambourine78Mute Cuica
55Splash Cymbal79Open Cuica
56Cowbell80Mute Triangle
57Crash Cymbal 281Open Triangle

Placing Instruments into an Enums file: 

I separated out the instrument keys and instruments placing them in an enums file:

Snippet of

This makes the program flexible to recognize how many instruments are listed, by using 'Instrument.values().length'. Adding instruments to the Instruments enums adds or changes the list of instruments in the app automatically.

Add a Listener to the Grid of Checkboxes

I created a listener for the instrument checkboxes, so the new beat would play instantly, instead of waiting for the user to press 'Start'.

I am still trying to figure out how to embed the Java app on an HTML page. Once I figure that out, I can place it here.  

View Source Code

Maybe after a few years of dabbling in little projects like this, I can become more proficiency in the language!

-T.J. Maher
 Sr. QA Engineer, Fitbit
 // Manual tester, 15 years
 // Automated tester for [ 4 ] months and counting

Please note: 'Adventures in Automation' is a personal blog about automated testing. It is not an official blog of

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