Problem Set 1: The Art of JFugue

package ps1;

public class FuguFugue {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub

	}

}

import org.jfugue.*;

	public static void main(String[] args) {
		Player player = new Player();
		player.play("C D E F G A B C6w");
	}

Understanding the Program

The first line declares an initializes a variable named player. It is initialized to a new Player object. The Player class is defined by JFugue. You can see its full interface in the JFugue documentation: http://www.jfugue.org/javadoc/org/jfugue/Player.html.

The Player class defines several methods that can be used to play music. The simplest one is to pass in a string to the play method. The string is what JFugue calls a MusicString. If you are a musician, you may be interested in all the things you can do with the MusicStrings. See the chapter from the JFugue book: http://www.jfugue.org/jfugue-chapter2.pdf (it is not necessary to read this, though, to complete this problem set).

The next line, player.play("C D E F G A B C6w"); invokes the play method on the player object created by the previous line. Method invocation is similar to calling a procedure, except the object is used before the method name. The most comparable Scheme syntax would be (play player "C D E F G A B C6w"). The parameter to the method is a String object. The java.lang.String datatype is built-in type for representing an immutable sequence of characters. Here, we create a String object using the special literal syntax, just putting the contents of the string in double quotes.

Experimenting with Java and JFugue

Copy the code below into your FuguFugue.java file, replacing the class definition as follows:

package ps1;
import org.jfugue.*;

public class FuguFugueOrig {
	private static String tune = "D Gqi F#i G B Aqi Gi A B Gqi Gi B D6 E6h Rq "
		+ "E6q D6qi B5i B5 G5 A5qi G5i A5 B5 G5qi E5i E5 D5 G5w+D5w+G4w";

	public static void playOldSong() {
		Player player = new Player();
		player.play("T125 I[GUITAR] " + tune);
	}

	public static void main(String[] args) {
		playOldSong();
	}

}

It plays a more interesting song that the scale in the first example, and puts the song in a separate method which is called by the main method.

To test your solution to Problem 2, you should modify the main procedure to pass in the parameter to playOldSong. The argument to main is an array of String objects that corresponds to the command line arguments to your program (Section 2.3 of the textbook introduces arrays). So, the first argument is args[0]. The problem is this argument is a String, and for the parameter to playOldSong we need an int (integer). The java.lang.Integer class provides the parseInt(String) static method that takes a String object as its input and returns an int object with the corresponding value. Thus,

     int num = Integer.parseInt(args[0]);

will initialize the integer variable num to the value corresponding to the first program argument. To set the program argument in Eclipse, select Run | Run Configurations which pops-up the Run Configurations dialog. Select the (x)= Arguments tab and enter the arguments you want in the Program arguments box.

Few wahoos are able to maintain a constant tempo as their enthusiasm brims while singing the song, so we want a way to increase the tempo. The T125 at the beginning of the music string sets the tempo to 125 beats per minute. By changing the number after the T we can set the tempo to any integer value. You can concatenate strings using the concatenation operator (+) like this:

     System.out.println("My favorite number is " + 2220);

The System.out.println method takes a String object as its input and prints out that string to the Java console. You may find it useful to use System.out.println to print the music string for Problem 3 so you can see it is correct.

Demonstrate your accelerateSong method by repeating the old song 5 times with tempo starting at 120 beats per minute and increasing 25% each repetition: accelerateSong(tune, 5, 120, 1.25); (where tune is a String variable initialized to the value of the song.

Note that the value after the T in a music string must be an integer. You can find the integer nearest a given floating point number using int Math.round(float). For example, Math.round(2.8) evaluates to the integer 3.

Print PDF