Make ConcurrentExpandableList an inner class

It is used only by the LogRecorder. Some day, we could migrate this
upstream to SciJava Common as a utility class. But for now, let's keep
it private, since it would be weird to depend on scijava-ui-swing just
to gain access to this class which is not Swing-specific.

Author: ctrueden

src/main/java/org/scijava/ui/swing/console/ConcurrentExpandableList.java

@@ -33,8 +33,15 @@
 
 import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.atomic.AtomicLong;
 import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
 
 import org.scijava.log.CallingClassUtils;
 import org.scijava.log.IgnoreAsCallingClass;
@@ -54,7 +61,8 @@
 @IgnoreAsCallingClass
 public class LogRecorder implements LogListener, Iterable<LogMessage> {
 
-	private ConcurrentExpandableList recorded = new ConcurrentExpandableList();
+	private ConcurrentExpandableList<LogMessage> recorded =
+		new ConcurrentExpandableList<>();
 
 	private List<Runnable> observers = new CopyOnWriteArrayList<>();
 
@@ -79,6 +87,7 @@ public void removeObserver(Runnable observer) {
 	 * {@link Iterator#hasNext()} will return true again, and
 	 * {@link Iterator#next()} will return the new log messages element.
 	 */
+	@Override
 	public Iterator<LogMessage> iterator() {
 		return recorded.iterator();
 	}
@@ -122,4 +131,74 @@ private void notifyListeners() {
 		for (Runnable listener : observers)
 			listener.run();
 	}
+
+	/**
+	 * This Container manages a list of items. Items can only be added to end of
+	 * the list. It's possible to add items, while iterating over the list.
+	 * Iterators never fail, and they will always be updated. Even if an element
+	 * is added after an iterator reached the end of the list,
+	 * {@link Iterator#hasNext()} will return true again, and
+	 * {@link Iterator#next()} will return the newly added element. This Container
+	 * is fully thread safe.
+	 *
+	 * @author Matthias Arzt
+	 */
+	private class ConcurrentExpandableList<T> implements Iterable<T> {
+
+		private final AtomicLong lastKey = new AtomicLong(0);
+
+		private long firstKey = 0;
+
+		private final Map<Long, T> map = new ConcurrentHashMap<>();
+
+		public Stream<T> stream() {
+			Spliterator<T> spliterator = Spliterators.spliteratorUnknownSize(
+					iterator(), Spliterator.ORDERED);
+			return StreamSupport.stream(spliterator, /* parallel */ false);
+		}
+
+		@Override
+		public Iterator<T> iterator() {
+			return new MyIterator(firstKey);
+		}
+
+		public Iterator<T> iteratorAtEnd() {
+			return new MyIterator(lastKey.get());
+		}
+
+		public long add(T value) {
+			long key = lastKey.getAndIncrement();
+			map.put(key, value);
+			return key;
+		}
+
+		public void clear() {
+			map.clear();
+			firstKey = lastKey.get();
+		}
+
+		private class MyIterator implements Iterator<T> {
+
+			private long nextIndex;
+
+			public MyIterator(long nextIndex) {
+				this.nextIndex = nextIndex;
+			}
+
+			@Override
+			public boolean hasNext() {
+				return map.containsKey(nextIndex);
+			}
+
+			@Override
+			public T next() {
+				T value = map.get(nextIndex);
+				if(value == null)
+					throw new NoSuchElementException();
+				nextIndex++;
+				return value;
+			}
+		}
+	}
+
 }

src/main/java/org/scijava/ui/swing/console/LogRecorder.java

@@ -23,7 +23,7 @@
  */
 public class LoggingDemo {
 
-	public static void main(String... args) throws InterruptedException {
+	public static void main(String... args) {
 		Context context = new Context();
 		UIService ui = context.service(UIService.class);
 		ui.showUI();
@@ -71,7 +71,7 @@ public void run() {
 			privateLogger.addLogListener(panel);
 
 			JFrame frame = new JFrame("Plugin that logs");
-			frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
+			frame.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
 			frame.setLayout(new MigLayout("","[grow]","[][grow]"));
 			frame.add(newButton("both log", () -> writeToLogger(logger)), "split");
 			frame.add(newButton("main log", () -> writeToLogger(logService)));
@@ -81,13 +81,13 @@ public void run() {
 			frame.setVisible(true);
 		}
 
-		private void writeToLogger(Logger logger) {
-			logger.error("Error message test");
-			logger.warn("Text describing a warning");
-			logger.info("An Information");
-			logger.debug("Something help debugging");
-			logger.trace("Trace everything");
-			logger.log(42, "Whats the best log level");
+		private void writeToLogger(Logger log) {
+			log.error("Error message test");
+			log.warn("Text describing a warning");
+			log.info("An Information");
+			log.debug("Something help debugging");
+			log.trace("Trace everything");
+			log.log(42, "Whats the best log level");
 		}
 
 		private Component newButton(String title, Runnable action) {