StaticKit: A Drum Kit as a Static Class

This class creates a simple drum rhythm. Its purpose is mainly to show how a program can be written with several static methods in the one class. This allows some complexity to be moved out of the main() method when code length gets a bit long. The notion of things being 'static' in Java can take a few attempts to fully understand, and hopefully this tutorial will provide one more step along the way.

A thing in Java which is declared to be static belongs only to the class it is in and cannot be instantiated (no copies of it can be made). Thus, if you only require (or want) one copy of a variable or method it can be declared static - perhaps think of it as always in one place. In this example there are static methods which can be called without instantiating them.

This is what the result sounds like:

Click here to view source ..

Let's have a closer look.

import jm.JMC;
import jm.midi.*;
import jm.util.*;
 * An example which generates a drum kit pattern
 * and writes to a MIDI file called StaticKit.mid
 * This version uses static methods in the one class.
 * @author Andrew Brown
public final class StaticKit implements JMC{
	public static void main(String[] args){
		Score pattern1 = new Score("Static class example"); 
		Part drums = new Part("Drums",0, 9); // 9 = MIDI channel 10
		Phrase phrBD = new Phrase();
		Phrase phrSD = new Phrase();
		Phrase phrHH = new Phrase();
		CPhrase phrEnd = new CPhrase();

The class starts in the normal way by importing, class declaration, and creating the main() method. The main method itself is always static, that is because we don't want more than one main() method, that would make no sense,the program can only start in one place. we next instantiate the jMusic Score, Part, Phrase, and CPhrase classes. In this section we lastly communicate with the user.

          //calling static methods below
		phrBD = KickPattern();
		phrSD = SnarePattern();
		phrHH = HatsPattern();
		phrEnd = EndPattern();

In this section of the class each of the phrase generation methods are called. Because we are calling them directly within the class, rather than calling them from an instance of the class, each of these methods needs to be static, as we will see below that they are.

          // loop the drum pattern
		int loopNum = 7;
		// add phrases to the instrument (part)
		// add the drum part to a score.
		// write the score to a MIDIfile
		Write.midi(pattern1, "StaticKit.mid");
The rest of the main() method proceeds in a standard fashion. The drum phrases are looped then packed into a jMusic score structure for export as a MIDI file.

     private static Phrase KickPattern() {
		// make bass drum
		Phrase phrase = new Phrase(0.0);
		for(int i=0;i<4;i++){
			Note note = new Note(36, C);
			Note rest = new Note(REST, C);
		return phrase;
The next method in this class is the KickPattern() method. This method is declared static so we can call it directly from the same class without having to put it in another class and instantiate that class, blah, blah, blah... The only other feature to look out for is that when the Phrase is declared in this method it is given a start time of 0.0, the phrase declared above had none because we knew it would be overwritten with this phrase.

Each of the snarePattern and hihatPattern methods look very similar to this one, so we won't show them here.

     private static CPhrase EndPattern() {
		// make crash ending
		CPhrase cphrase = new CPhrase();
		int[] pitchArray1a = {36,49}; // kick and crash cymbal
		cphrase.addChord(pitchArray1a, SB);
		return cphrase;
The EndPattern() method is different in two ways. Firstly, it uses a CPhrase rather than a Phrase so that we can conveniently have have two drums sounding together. Secondly, the CPhrase is declared with no startTime argument. This means that when it is added to the Part it will be placed at the end of the other phrases. This is also convenient because it allows us to make the earlier patterns of any length or have any number of loops and the CPhrase will always be placed at the end.

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