play square wave from JRuby.

PlaySquareWave.rb

include Java

java_import javax.sound.sampled.AudioFormat
java_import javax.sound.sampled.DataLine
java_import javax.sound.sampled.SourceDataLine
java_import javax.sound.sampled.AudioSystem

SAMPLE_RATE = 44100
audio_format = AudioFormat.new(SAMPLE_RATE, 8, 1, true, true)
info = DataLine::Info.new(SourceDataLine.java_class, audio_format)
line = AudioSystem::getLine(info)
frequency = 440
amplitude = SAMPLE_RATE / (frequency * 2)
buf = []
SAMPLE_RATE.times do |i|
  r = i / amplitude
  buf[i] = (r % 2 == 0) ? 5 : -5
end
line.open
line.start
jbuf = buf.to_java(:byte)
line.write(jbuf, 0, jbuf.length)
line.drain