Add few assertions in the code, minor changes

webcam-capture/src/example/java/com/github/sarxos/webcam/example/CalculateFPSExample.java

@@ -0,0 +1,37 @@
+package com.github.sarxos.webcam.example;
+
+import com.github.sarxos.webcam.Webcam;
+import com.github.sarxos.webcam.log.WebcamLogConfigurator;
+
+
+public class CalculateFPSExample {
+
+	public static void main(String[] args) {
+
+		WebcamLogConfigurator.configure("src/example/resources/logback.xml");
+
+		long t1 = 0;
+		long t2 = 0;
+
+		int p = 10;
+		int r = 5;
+
+		Webcam webcam = Webcam.getDefault();
+
+		for (int k = 0; k < p; k++) {
+
+			webcam.open();
+			webcam.getImage();
+
+			t1 = System.currentTimeMillis();
+			for (int i = 0; ++i <= r; webcam.getImage()) {
+			}
+			t2 = System.currentTimeMillis();
+
+			System.out.println("FPS " + k + ": " + (1000 * r / (t2 - t1 + 1)));
+
+			webcam.close();
+		}
+
+	}
+}

webcam-capture/src/example/resources/logback.xml

@@ -4,7 +4,7 @@
 			<Pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</Pattern>
 		</layout>
 	</appender>
-	<root level="warn">
+	<root level="error">
 		<appender-ref ref="STDOUT" />
 	</root>
 </configuration>

webcam-capture/src/main/java/com/github/sarxos/webcam/Webcam.java

@@ -165,6 +165,8 @@ public boolean open(boolean async) {
 
 		if (open.compareAndSet(false, true)) {
 
+			assert updater != null;
+
 			WebcamOpenTask task = new WebcamOpenTask(driver, device);
 			try {
 				task.open();
@@ -216,6 +218,8 @@ public boolean close() {
 
 		if (open.compareAndSet(true, false)) {
 
+			assert updater != null;
+
 			// close webcam
 
 			WebcamCloseTask task = new WebcamCloseTask(driver, device);
@@ -293,6 +297,7 @@ public Dimension[] getViewSizes() {
 	 * @param sizes the array of custom resolutions to be supported by webcam
 	 */
 	public void setCustomViewSizes(Dimension[] sizes) {
+		assert customSizes != null;
 		if (sizes == null) {
 			customSizes.clear();
 			return;
@@ -301,6 +306,7 @@ public void setCustomViewSizes(Dimension[] sizes) {
 	}
 
 	public Dimension[] getCustomViewSizes() {
+		assert customSizes != null;
 		return customSizes.toArray(new Dimension[customSizes.size()]);
 	}
 
@@ -334,6 +340,9 @@ public void setViewSize(Dimension size) {
 		Dimension[] predefined = getViewSizes();
 		Dimension[] custom = getCustomViewSizes();
 
+		assert predefined != null;
+		assert custom != null;
+
 		boolean ok = false;
 		for (Dimension d : predefined) {
 			if (d.width == size.width && d.height == size.height) {
@@ -394,6 +403,8 @@ public BufferedImage getImage() {
 		long t1 = 0;
 		long t2 = 0;
 
+		assert updater != null;
+
 		if (asynchronous) {
 			return updater.getImage();
 		} else {
@@ -422,13 +433,15 @@ public BufferedImage getImage() {
 	}
 
 	public boolean isImageNew() {
+		assert updater != null;
 		if (asynchronous) {
 			return updater.isImageNew();
 		}
 		return true;
 	}
 
 	protected double getFPS() {
+		assert updater != null;
 		if (asynchronous) {
 			return updater.getFPS();
 		} else {
@@ -456,14 +469,22 @@ public ByteBuffer getImageBytes() {
 			return null;
 		}
 
+		assert driver != null;
+		assert device != null;
+
 		// some devices can support direct image buffers, and for those call
 		// processor task, and for those which does not support direct image
 		// buffers, just convert image to RGB byte array
 
 		if (device instanceof BufferAccess) {
 			return new WebcamReadBufferTask(driver, device).getBuffer();
 		} else {
-			return ByteBuffer.wrap(ImageUtils.toRawByteArray(getImage()));
+			BufferedImage image = getImage();
+			if (image != null) {
+				return ByteBuffer.wrap(ImageUtils.toRawByteArray(image));
+			} else {
+				return null;
+			}
 		}
 	}
 
@@ -474,6 +495,9 @@ public ByteBuffer getImageBytes() {
 	 */
 	private boolean isReady() {
 
+		assert disposed != null;
+		assert open != null;
+
 		if (disposed.get()) {
 			LOG.warn("Cannot get image, webcam has been already disposed");
 			return false;
@@ -495,7 +519,7 @@ private boolean isReady() {
 	 * interval for webcam devices to be discovered. By default this time is set
 	 * to 1 minute.
 	 * 
-	 * @return List of webcams existing in the ssytem
+	 * @return List of webcams existing in the system
 	 * @throws WebcamException when something is wrong
 	 * @see Webcam#getWebcams(long, TimeUnit)
 	 */
@@ -518,9 +542,13 @@ public static List<Webcam> getWebcams() throws WebcamException {
 	 * @param timeout the time to wait for webcam devices to be discovered
 	 * @return List of webcams existing in the ssytem
 	 * @throws WebcamException when something is wrong
+	 * @throws IllegalArgumentException when timeout is negative
 	 * @see Webcam#getWebcams(long, TimeUnit)
 	 */
 	public static List<Webcam> getWebcams(long timeout) throws TimeoutException, WebcamException {
+		if (timeout < 0) {
+			throw new IllegalArgumentException(String.format("Timeout cannot be negative (%d)", timeout));
+		}
 		return getWebcams(timeout, TimeUnit.MILLISECONDS);
 	}
 
@@ -533,12 +561,22 @@ public static List<Webcam> getWebcams(long timeout) throws TimeoutException, Web
 	 * @return List of webcams
 	 * @throws TimeoutException when timeout has been exceeded
 	 * @throws WebcamException when something is wrong
+	 * @throws IllegalArgumentException when timeout is negative or tunit null
 	 */
 	public static synchronized List<Webcam> getWebcams(long timeout, TimeUnit tunit) throws TimeoutException, WebcamException {
 
+		if (timeout < 0) {
+			throw new IllegalArgumentException(String.format("Timeout cannot be negative (%d)", timeout));
+		}
+		if (tunit == null) {
+			throw new IllegalArgumentException("Time unit cannot be null!");
+		}
+
 		WebcamDiscoveryService discovery = getDiscoveryService();
-		List<Webcam> webcams = discovery.getWebcams(timeout, tunit);
 
+		assert discovery != null;
+
+		List<Webcam> webcams = discovery.getWebcams(timeout, tunit);
 		if (!discovery.isRunning()) {
 			discovery.start();
 		}
@@ -571,9 +609,13 @@ public static Webcam getDefault() throws WebcamException {
 	 * @return Default webcam (first from the list)
 	 * @throws TimeoutException when discovery timeout has been exceeded
 	 * @throws WebcamException if something is really wrong
+	 * @throws IllegalArgumentException when timeout is negative
 	 * @see Webcam#getWebcams(long)
 	 */
 	public static Webcam getDefault(long timeout) throws TimeoutException, WebcamException {
+		if (timeout < 0) {
+			throw new IllegalArgumentException(String.format("Timeout cannot be negative (%d)", timeout));
+		}
 		return getDefault(timeout, TimeUnit.MILLISECONDS);
 	}
 
@@ -585,19 +627,22 @@ public static Webcam getDefault(long timeout) throws TimeoutException, WebcamExc
 	 * @return Default webcam (first from the list)
 	 * @throws TimeoutException when discovery timeout has been exceeded
 	 * @throws WebcamException if something is really wrong
+	 * @throws IllegalArgumentException when timeout is negative or tunit null
 	 * @see Webcam#getWebcams(long, TimeUnit)
 	 */
 	public static Webcam getDefault(long timeout, TimeUnit tunit) throws TimeoutException, WebcamException {
 
 		if (timeout < 0) {
-			throw new IllegalArgumentException("Timeout cannot be negative");
+			throw new IllegalArgumentException(String.format("Timeout cannot be negative (%d)", timeout));
 		}
 		if (tunit == null) {
 			throw new IllegalArgumentException("Time unit cannot be null!");
 		}
 
 		List<Webcam> webcams = getWebcams(timeout, tunit);
 
+		assert webcams != null;
+
 		if (!webcams.isEmpty()) {
 			return webcams.get(0);
 		}
@@ -615,6 +660,7 @@ public static Webcam getDefault(long timeout, TimeUnit tunit) throws TimeoutExce
 	 * @return Name
 	 */
 	public String getName() {
+		assert device != null;
 		return device.getName();
 	}
 
@@ -633,20 +679,23 @@ public boolean addWebcamListener(WebcamListener l) {
 		if (l == null) {
 			throw new IllegalArgumentException("Webcam listener cannot be null!");
 		}
+		assert listeners != null;
 		return listeners.add(l);
 	}
 
 	/**
 	 * @return All webcam listeners
 	 */
 	public WebcamListener[] getWebcamListeners() {
+		assert listeners != null;
 		return listeners.toArray(new WebcamListener[listeners.size()]);
 	}
 
 	/**
 	 * @return Number of webcam listeners
 	 */
 	public int getWebcamListenersCount() {
+		assert listeners != null;
 		return listeners.size();
 	}
 
@@ -657,6 +706,7 @@ public int getWebcamListenersCount() {
 	 * @return True if listener has been removed, false otherwise
 	 */
 	public boolean removeWebcamListener(WebcamListener l) {
+		assert listeners != null;
 		return listeners.remove(l);
 	}
 
@@ -713,12 +763,12 @@ public static synchronized void setDriver(WebcamDriver driver) {
 	 */
 	public static synchronized void setDriver(Class<? extends WebcamDriver> driverClass) {
 
-		resetDriver();
-
 		if (driverClass == null) {
 			throw new IllegalArgumentException("Webcam driver class cannot be null!");
 		}
 
+		resetDriver();
+
 		try {
 			driver = driverClass.newInstance();
 		} catch (InstantiationException e) {
@@ -780,6 +830,7 @@ public static void registerDriver(String clazzName) {
 	 * @return Underlying webcam device instance
 	 */
 	public WebcamDevice getDevice() {
+		assert device != null;
 		return device;
 	}
 
@@ -789,6 +840,12 @@ public WebcamDevice getDevice() {
 	 */
 	protected void dispose() {
 
+		assert disposed != null;
+		assert open != null;
+		assert driver != null;
+		assert device != null;
+		assert listeners != null;
+
 		if (!disposed.compareAndSet(false, true)) {
 			return;
 		}

webcam-capture/src/main/java/com/github/sarxos/webcam/WebcamDiscoveryService.java

@@ -1,5 +1,6 @@
 package com.github.sarxos.webcam;
 
+import java.lang.Thread.UncaughtExceptionHandler;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Iterator;
@@ -18,11 +19,11 @@
 import org.slf4j.LoggerFactory;
 
 
-public class WebcamDiscoveryService implements Runnable {
+public class WebcamDiscoveryService implements Runnable, UncaughtExceptionHandler {
 
 	private static final Logger LOG = LoggerFactory.getLogger(WebcamDiscoveryService.class);
 
-	private static final class WebcamsDiscovery implements Callable<List<Webcam>>, ThreadFactory {
+	private static final class WebcamsDiscovery implements Callable<List<Webcam>>, ThreadFactory, UncaughtExceptionHandler {
 
 		private final WebcamDriver driver;
 
@@ -39,8 +40,14 @@ public List<Webcam> call() throws Exception {
 		public Thread newThread(Runnable r) {
 			Thread t = new Thread(r, "webcam-discovery-service");
 			t.setDaemon(true);
+			t.setUncaughtExceptionHandler(this);
 			return t;
 		}
+
+		@Override
+		public void uncaughtException(Thread t, Throwable e) {
+			LOG.error(String.format("Exception in thread %s", t.getName()), e);
+		}
 	}
 
 	private final WebcamDriver driver;
@@ -53,6 +60,11 @@ public Thread newThread(Runnable r) {
 	private Thread runner = null;
 
 	protected WebcamDiscoveryService(WebcamDriver driver) {
+
+		if (driver == null) {
+			throw new IllegalArgumentException("Driver cannot be null!");
+		}
+
 		this.driver = driver;
 		this.support = (WebcamDiscoverySupport) (driver instanceof WebcamDiscoverySupport ? driver : null);
 	}
@@ -320,6 +332,7 @@ public synchronized void start() {
 
 		runner = new Thread(this, "webcam-discovery-service");
 		runner.setDaemon(true);
+		runner.setUncaughtExceptionHandler(this);
 		runner.start();
 	}
 
@@ -353,4 +366,9 @@ protected synchronized void shutdown() {
 			WebcamDeallocator.unstore();
 		}
 	}
+
+	@Override
+	public void uncaughtException(Thread t, Throwable e) {
+		LOG.error(String.format("Exception in thread %s", t.getName()), e);
+	}
 }

webcam-capture/src/main/java/com/github/sarxos/webcam/WebcamPanel.java

@@ -66,6 +66,9 @@ public class DefaultPainter implements Painter {
 		@Override
 		public void paintPanel(WebcamPanel owner, Graphics2D g2) {
 
+			assert owner != null;
+			assert g2 != null;
+
 			g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
 			g2.setBackground(Color.BLACK);
 			g2.fillRect(0, 0, getWidth(), getHeight());