public class SquareWave extends Thread {
	private Regul regul;
	private int sign = 1;
	
	private AmplitudeMonitor ampMon = new AmplitudeMonitor();
	
	// Internal AmplitudeMonitor class
	// Constructor not necessary
	private class AmplitudeMonitor {
		private double amp = 0.0;
		
		// Synchronized access methods. The amplitude should always be non-negative.
		public synchronized double getAmp() {
			return amp;
		}
		public synchronized void setAmp(double amp) {
			this.amp = Math.max(amp, 0);
		}
	}
	
	// Constructor
	public SquareWave(Regul regul, int priority) {
		this.regul = regul;
		setPriority(priority);
	}
	
	// Public methods to decrease and increase the amplitude by delta. Called from Buttons
	// Should be synchronized on ampMon. Should also call the setRef method in Regul
	public void incAmp(double delta) {
		synchronized (ampMon) {
			ampMon.setAmp(ampMon.getAmp() + delta);
		}
		setRef();
	}
	
	public void decAmp(double delta) {
		incAmp(-delta);
	}
	
	private void setRef() {
		regul.setRef(sign*ampMon.getAmp());
	}
	
	// run method
	public void run() {
		final long h = 10000; // period (ms)
		try {
			while (!Thread.interrupted()) {
				sign = -sign;
				setRef();
				Thread.sleep(h);
			}
		} catch (InterruptedException e) {
			// Requested to stop
		}
		System.out.println("SquareWave stopped.");
	}
}