From a0b24f74a56adc13f986f0770633aacc776dac71 Mon Sep 17 00:00:00 2001
From: Robert von Burg <eitch@eitchnet.ch>
Date: Tue, 19 May 2020 11:16:53 +0200
Subject: [PATCH] [Fix] Fixed concurrent modification exception in
 SynchronizedCollections

---
 .../collections/SynchronizedCollections.java  | 146 ++++++++--------
 .../SynchronizedMapOfListsTest.java           | 160 +++++++++++++++++
 .../SynchronizedMapOfMapsTest.java            | 162 ++++++++++++++++++
 .../SynchronizedMapOfSetsTest.java            | 160 +++++++++++++++++
 4 files changed, 555 insertions(+), 73 deletions(-)
 create mode 100644 li.strolch.utils/src/test/java/li/strolch/utils/collections/SynchronizedMapOfListsTest.java
 create mode 100644 li.strolch.utils/src/test/java/li/strolch/utils/collections/SynchronizedMapOfMapsTest.java
 create mode 100644 li.strolch.utils/src/test/java/li/strolch/utils/collections/SynchronizedMapOfSetsTest.java

diff --git a/li.strolch.utils/src/main/java/li/strolch/utils/collections/SynchronizedCollections.java b/li.strolch.utils/src/main/java/li/strolch/utils/collections/SynchronizedCollections.java
index bb83ef860..acb4c4116 100644
--- a/li.strolch.utils/src/main/java/li/strolch/utils/collections/SynchronizedCollections.java
+++ b/li.strolch.utils/src/main/java/li/strolch/utils/collections/SynchronizedCollections.java
@@ -29,7 +29,7 @@ public class SynchronizedCollections {
 
 		SynchronizedMapOfLists(MapOfLists<T, U> m) {
 			this.m = m;
-			this.mutex = new Object();
+			this.mutex = this;
 		}
 
 		@Override
@@ -174,7 +174,7 @@ public class SynchronizedCollections {
 
 		SynchronizedMapOfMaps(MapOfMaps<T, U, V> m) {
 			this.m = m;
-			this.mutex = new Object();
+			this.mutex = this;
 		}
 
 		@Override
@@ -341,7 +341,7 @@ public class SynchronizedCollections {
 
 		public SynchronizedMapOfSets(MapOfSets<T, U> m) {
 			this.m = m;
-			this.mutex = new Object();
+			this.mutex = this;
 		}
 
 		@Override
@@ -507,35 +507,35 @@ public class SynchronizedCollections {
 
 		@Override
 		public int size() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.size();
 			}
 		}
 
 		@Override
 		public boolean isEmpty() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.isEmpty();
 			}
 		}
 
 		@Override
 		public boolean contains(Object o) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.contains(o);
 			}
 		}
 
 		@Override
 		public Object[] toArray() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.toArray();
 			}
 		}
 
 		@Override
 		public <T> T[] toArray(T[] a) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.toArray(a);
 			}
 		}
@@ -547,70 +547,70 @@ public class SynchronizedCollections {
 
 		@Override
 		public boolean add(E e) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.add(e);
 			}
 		}
 
 		@Override
 		public boolean remove(Object o) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.remove(o);
 			}
 		}
 
 		@Override
 		public boolean containsAll(Collection<?> coll) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.containsAll(coll);
 			}
 		}
 
 		@Override
 		public boolean addAll(Collection<? extends E> coll) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.addAll(coll);
 			}
 		}
 
 		@Override
 		public boolean removeAll(Collection<?> coll) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.removeAll(coll);
 			}
 		}
 
 		@Override
 		public boolean retainAll(Collection<?> coll) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.retainAll(coll);
 			}
 		}
 
 		@Override
 		public void clear() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				c.clear();
 			}
 		}
 
 		@Override
 		public String toString() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.toString();
 			}
 		}
 
 		@Override
 		public void forEach(Consumer<? super E> consumer) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				c.forEach(consumer);
 			}
 		}
 
 		@Override
 		public boolean removeIf(Predicate<? super E> filter) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.removeIf(filter);
 			}
 		}
@@ -631,7 +631,7 @@ public class SynchronizedCollections {
 		}
 
 		private void writeObject(ObjectOutputStream s) throws IOException {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				s.defaultWriteObject();
 			}
 		}
@@ -650,63 +650,63 @@ public class SynchronizedCollections {
 		public boolean equals(Object o) {
 			if (this == o)
 				return true;
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return list.equals(o);
 			}
 		}
 
 		@Override
 		public int hashCode() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return list.hashCode();
 			}
 		}
 
 		@Override
 		public E get(int index) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return list.get(index);
 			}
 		}
 
 		@Override
 		public E set(int index, E element) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return list.set(index, element);
 			}
 		}
 
 		@Override
 		public void add(int index, E element) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				list.add(index, element);
 			}
 		}
 
 		@Override
 		public E remove(int index) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return list.remove(index);
 			}
 		}
 
 		@Override
 		public int indexOf(Object o) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return list.indexOf(o);
 			}
 		}
 
 		@Override
 		public int lastIndexOf(Object o) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return list.lastIndexOf(o);
 			}
 		}
 
 		@Override
 		public boolean addAll(int index, Collection<? extends E> c) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return list.addAll(index, c);
 			}
 		}
@@ -723,21 +723,21 @@ public class SynchronizedCollections {
 
 		@Override
 		public List<E> subList(int fromIndex, int toIndex) {
-			synchronized (mutex) {
-				return new SynchronizedList<>(list.subList(fromIndex, toIndex), mutex);
+			synchronized (this.mutex) {
+				return new SynchronizedList<>(list.subList(fromIndex, toIndex), this.mutex);
 			}
 		}
 
 		@Override
 		public void replaceAll(UnaryOperator<E> operator) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				list.replaceAll(operator);
 			}
 		}
 
 		@Override
 		public void sort(Comparator<? super E> c) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				list.sort(c);
 			}
 		}
@@ -753,14 +753,14 @@ public class SynchronizedCollections {
 		public boolean equals(Object o) {
 			if (this == o)
 				return true;
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.equals(o);
 			}
 		}
 
 		@Override
 		public int hashCode() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return c.hashCode();
 			}
 		}
@@ -777,42 +777,42 @@ public class SynchronizedCollections {
 
 		@Override
 		public Comparator<? super E> comparator() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return ss.comparator();
 			}
 		}
 
 		@Override
 		public SortedSet<E> subSet(E fromElement, E toElement) {
-			synchronized (mutex) {
-				return new SynchronizedSortedSet<>(ss.subSet(fromElement, toElement), mutex);
+			synchronized (this.mutex) {
+				return new SynchronizedSortedSet<>(ss.subSet(fromElement, toElement), this.mutex);
 			}
 		}
 
 		@Override
 		public SortedSet<E> headSet(E toElement) {
-			synchronized (mutex) {
-				return new SynchronizedSortedSet<>(ss.headSet(toElement), mutex);
+			synchronized (this.mutex) {
+				return new SynchronizedSortedSet<>(ss.headSet(toElement), this.mutex);
 			}
 		}
 
 		@Override
 		public SortedSet<E> tailSet(E fromElement) {
-			synchronized (mutex) {
-				return new SynchronizedSortedSet<>(ss.tailSet(fromElement), mutex);
+			synchronized (this.mutex) {
+				return new SynchronizedSortedSet<>(ss.tailSet(fromElement), this.mutex);
 			}
 		}
 
 		@Override
 		public E first() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return ss.first();
 			}
 		}
 
 		@Override
 		public E last() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return ss.last();
 			}
 		}
@@ -829,55 +829,55 @@ public class SynchronizedCollections {
 		}
 
 		public int size() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.size();
 			}
 		}
 
 		public boolean isEmpty() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.isEmpty();
 			}
 		}
 
 		public boolean containsKey(Object key) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.containsKey(key);
 			}
 		}
 
 		public boolean containsValue(Object value) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.containsValue(value);
 			}
 		}
 
 		public V get(Object key) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.get(key);
 			}
 		}
 
 		public V put(K key, V value) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.put(key, value);
 			}
 		}
 
 		public V remove(Object key) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.remove(key);
 			}
 		}
 
 		public void putAll(Map<? extends K, ? extends V> map) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				m.putAll(map);
 			}
 		}
 
 		public void clear() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				m.clear();
 			}
 		}
@@ -887,25 +887,25 @@ public class SynchronizedCollections {
 		private transient Collection<V> values;
 
 		public Set<K> keySet() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				if (keySet == null)
-					keySet = new SynchronizedSet<>(m.keySet(), mutex);
+					keySet = new SynchronizedSet<>(m.keySet(), this.mutex);
 				return keySet;
 			}
 		}
 
 		public Set<Map.Entry<K, V>> entrySet() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				if (entrySet == null)
-					entrySet = new SynchronizedSet<>(m.entrySet(), mutex);
+					entrySet = new SynchronizedSet<>(m.entrySet(), this.mutex);
 				return entrySet;
 			}
 		}
 
 		public Collection<V> values() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				if (values == null)
-					values = new SynchronizedCollection<>(m.values(), mutex);
+					values = new SynchronizedCollection<>(m.values(), this.mutex);
 				return values;
 			}
 		}
@@ -913,102 +913,102 @@ public class SynchronizedCollections {
 		public boolean equals(Object o) {
 			if (this == o)
 				return true;
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.equals(o);
 			}
 		}
 
 		public int hashCode() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.hashCode();
 			}
 		}
 
 		public String toString() {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.toString();
 			}
 		}
 
 		@Override
 		public V getOrDefault(Object k, V defaultValue) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.getOrDefault(k, defaultValue);
 			}
 		}
 
 		@Override
 		public void forEach(BiConsumer<? super K, ? super V> action) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				m.forEach(action);
 			}
 		}
 
 		@Override
 		public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				m.replaceAll(function);
 			}
 		}
 
 		@Override
 		public V putIfAbsent(K key, V value) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.putIfAbsent(key, value);
 			}
 		}
 
 		@Override
 		public boolean remove(Object key, Object value) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.remove(key, value);
 			}
 		}
 
 		@Override
 		public boolean replace(K key, V oldValue, V newValue) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.replace(key, oldValue, newValue);
 			}
 		}
 
 		@Override
 		public V replace(K key, V value) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.replace(key, value);
 			}
 		}
 
 		@Override
 		public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.computeIfAbsent(key, mappingFunction);
 			}
 		}
 
 		@Override
 		public V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.computeIfPresent(key, remappingFunction);
 			}
 		}
 
 		@Override
 		public V compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.compute(key, remappingFunction);
 			}
 		}
 
 		@Override
 		public V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				return m.merge(key, value, remappingFunction);
 			}
 		}
 
 		private void writeObject(ObjectOutputStream s) throws IOException {
-			synchronized (mutex) {
+			synchronized (this.mutex) {
 				s.defaultWriteObject();
 			}
 		}
diff --git a/li.strolch.utils/src/test/java/li/strolch/utils/collections/SynchronizedMapOfListsTest.java b/li.strolch.utils/src/test/java/li/strolch/utils/collections/SynchronizedMapOfListsTest.java
new file mode 100644
index 000000000..b2b38b4aa
--- /dev/null
+++ b/li.strolch.utils/src/test/java/li/strolch/utils/collections/SynchronizedMapOfListsTest.java
@@ -0,0 +1,160 @@
+package li.strolch.utils.collections;
+
+import static li.strolch.utils.collections.SynchronizedCollections.synchronizedMapOfLists;
+import static org.junit.Assert.*;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Set;
+import java.util.UUID;
+import java.util.concurrent.*;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class SynchronizedMapOfListsTest {
+
+	private static final Logger logger = LoggerFactory.getLogger(SynchronizedMapOfListsTest.class);
+
+	private ExecutorService executorService;
+
+	@Before
+	public void before() {
+		this.executorService = Executors.newCachedThreadPool();
+	}
+
+	@Test
+	public void shouldForEach() throws ExecutionException, InterruptedException {
+
+		MapOfLists<String, String> mapOfLists = buildMapOfLists();
+		AtomicBoolean run = new AtomicBoolean(false);
+		Callable<Boolean> addTask = () -> addToMap(mapOfLists, run);
+
+		Callable<Boolean> iterateTask = () -> {
+			for (; ; ) {
+				if (run.get())
+					break;
+			}
+
+			while (run.get()) {
+				mapOfLists.forEach((s, list) -> list.forEach(s1 -> logger.info(s + " " + s1)));
+				mapOfLists.getList("Resource").forEach(s1 -> logger.info("  " + s1));
+			}
+
+			return true;
+		};
+
+		runTest(addTask, iterateTask, run);
+	}
+
+	@Test
+	public void shouldIterate() throws ExecutionException, InterruptedException {
+
+		MapOfLists<String, String> mapOfLists = buildMapOfLists();
+		AtomicBoolean run = new AtomicBoolean(false);
+		Callable<Boolean> addTask = () -> addToMap(mapOfLists, run);
+		Callable<Boolean> iterateTask = () -> {
+			for (; ; ) {
+				if (run.get())
+					break;
+			}
+
+			while (run.get()) {
+				Set<String> types = mapOfLists.keySet();
+				for (String type : types) {
+					synchronized (mapOfLists) {
+						for (String id : mapOfLists.getList(type)) {
+							logger.info(type + " " + id);
+						}
+					}
+				}
+
+				synchronized (mapOfLists) {
+					List<String> resources = mapOfLists.getList("Resource");
+					for (String value : resources) {
+						logger.info("Resource: value: " + value);
+					}
+				}
+			}
+
+			return true;
+		};
+
+		runTest(addTask, iterateTask, run);
+	}
+
+	private void runTest(Callable<Boolean> addTask, Callable<Boolean> iterateTask, AtomicBoolean run)
+			throws InterruptedException, ExecutionException {
+
+		Future<Boolean> task0 = this.executorService.submit(addTask);
+		Future<Boolean> task1 = this.executorService.submit(iterateTask);
+		Future<Boolean> task2 = this.executorService.submit(iterateTask);
+		Future<Boolean> task3 = this.executorService.submit(iterateTask);
+		Future<Boolean> task4 = this.executorService.submit(iterateTask);
+		Future<Boolean> task5 = this.executorService.submit(iterateTask);
+
+		run.set(true);
+		Thread.sleep(1000L);
+		run.set(false);
+
+		Boolean result0 = task0.get();
+		Boolean result1 = task1.get();
+		Boolean result2 = task2.get();
+		Boolean result3 = task3.get();
+		Boolean result4 = task4.get();
+		Boolean result5 = task5.get();
+
+		assertTrue(result0);
+		assertTrue(result1);
+		assertTrue(result2);
+		assertTrue(result3);
+		assertTrue(result4);
+		assertTrue(result5);
+	}
+
+	private Boolean addToMap(MapOfLists<String, String> mapOfLists, AtomicBoolean run) {
+		for (; ; ) {
+			if (run.get())
+				break;
+		}
+
+		while (run.get()) {
+			addElement(mapOfLists, "Resource", UUID.randomUUID().toString());
+			addElement(mapOfLists, "Resource", UUID.randomUUID().toString());
+			addElement(mapOfLists, "Order", UUID.randomUUID().toString());
+			addElement(mapOfLists, "Order", UUID.randomUUID().toString());
+			addElement(mapOfLists, "Order", UUID.randomUUID().toString());
+			addElement(mapOfLists, "Activity", UUID.randomUUID().toString());
+			addElement(mapOfLists, "Activity", UUID.randomUUID().toString());
+
+			mapOfLists.removeElement("Resource", "Ball");
+			mapOfLists.removeElement("Order", "ToStock");
+			mapOfLists.removeElement("Activity", "ToStock");
+		}
+
+		return true;
+	}
+
+	private void addElement(MapOfLists<String, String> mapOfLists, String type, String id) {
+		logger.info("Adding " + type + " " + id);
+		mapOfLists.addElement(type, id);
+	}
+
+	private MapOfLists<String, String> buildMapOfLists() {
+		MapOfLists<String, String> mapOfLists = synchronizedMapOfLists(new MapOfLists<>(true));
+		mapOfLists.addElement("Resource", "Ball");
+		mapOfLists.addElement("Resource", "Car");
+		mapOfLists.addElement("Order", "StockOrder");
+		mapOfLists.addElement("Order", "ToStock");
+		mapOfLists.addElement("Order", "FromStock");
+		mapOfLists.addElement("Activity", "FromStock");
+		mapOfLists.addElement("Activity", "ToStock");
+
+		assertEquals(Arrays.asList("Ball", "Car"), mapOfLists.getList("Resource"));
+		assertNull(mapOfLists.getList("xxx"));
+		return mapOfLists;
+	}
+}
diff --git a/li.strolch.utils/src/test/java/li/strolch/utils/collections/SynchronizedMapOfMapsTest.java b/li.strolch.utils/src/test/java/li/strolch/utils/collections/SynchronizedMapOfMapsTest.java
new file mode 100644
index 000000000..a43877417
--- /dev/null
+++ b/li.strolch.utils/src/test/java/li/strolch/utils/collections/SynchronizedMapOfMapsTest.java
@@ -0,0 +1,162 @@
+package li.strolch.utils.collections;
+
+import static li.strolch.utils.collections.SynchronizedCollections.synchronizedMapOfMaps;
+import static org.junit.Assert.*;
+
+import java.util.Map;
+import java.util.Set;
+import java.util.UUID;
+import java.util.concurrent.*;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class SynchronizedMapOfMapsTest {
+
+	private static final Logger logger = LoggerFactory.getLogger(SynchronizedMapOfMapsTest.class);
+
+	private ExecutorService executorService;
+
+	@Before
+	public void before() {
+		this.executorService = Executors.newCachedThreadPool();
+	}
+
+	@Test
+	public void shouldForEach() throws ExecutionException, InterruptedException {
+
+		MapOfMaps<String, String, String> mapOfMaps = buildMapOfMaps();
+		AtomicBoolean run = new AtomicBoolean(false);
+		Callable<Boolean> addTask = () -> addToMap(mapOfMaps, run);
+
+		Callable<Boolean> iterateTask = () -> {
+			for (; ; ) {
+				if (run.get())
+					break;
+			}
+
+			while (run.get()) {
+				mapOfMaps.forEach(
+						(s, subTypeMap) -> subTypeMap.forEach((s1, s2) -> logger.info(s + " " + s1 + " " + s2)));
+				mapOfMaps.getMap("Resource").forEach((s1, s2) -> logger.info("  " + s1 + " " + s2));
+			}
+
+			return true;
+		};
+
+		runTest(addTask, iterateTask, run);
+	}
+
+	@Test
+	public void shouldIterate() throws ExecutionException, InterruptedException {
+
+		MapOfMaps<String, String, String> mapOfMaps = buildMapOfMaps();
+		AtomicBoolean run = new AtomicBoolean(false);
+		Callable<Boolean> addTask = () -> addToMap(mapOfMaps, run);
+		Callable<Boolean> iterateTask = () -> {
+			for (; ; ) {
+				if (run.get())
+					break;
+			}
+
+			while (run.get()) {
+				Set<String> types = mapOfMaps.keySet();
+				for (String type : types) {
+					Map<String, String> subTypeMap = mapOfMaps.getMap(type);
+					Set<String> subTypes = subTypeMap.keySet();
+					synchronized (mapOfMaps) {
+						for (String subType : subTypes) {
+							logger.info(type + " " + subType + " " + mapOfMaps.getElement(type, subType));
+						}
+					}
+				}
+
+				synchronized (mapOfMaps) {
+					Map<String, String> resources = mapOfMaps.getMap("Resource");
+					for (String value : resources.values()) {
+						logger.info("Resource: value: " + value);
+					}
+				}
+			}
+
+			return true;
+		};
+
+		runTest(addTask, iterateTask, run);
+	}
+
+	private void runTest(Callable<Boolean> addTask, Callable<Boolean> iterateTask, AtomicBoolean run)
+			throws InterruptedException, ExecutionException {
+
+		Future<Boolean> task0 = this.executorService.submit(addTask);
+		Future<Boolean> task1 = this.executorService.submit(iterateTask);
+		Future<Boolean> task2 = this.executorService.submit(iterateTask);
+		Future<Boolean> task3 = this.executorService.submit(iterateTask);
+		Future<Boolean> task4 = this.executorService.submit(iterateTask);
+		Future<Boolean> task5 = this.executorService.submit(iterateTask);
+
+		run.set(true);
+		Thread.sleep(1000L);
+		run.set(false);
+
+		Boolean result0 = task0.get();
+		Boolean result1 = task1.get();
+		Boolean result2 = task2.get();
+		Boolean result3 = task3.get();
+		Boolean result4 = task4.get();
+		Boolean result5 = task5.get();
+
+		assertTrue(result0);
+		assertTrue(result1);
+		assertTrue(result2);
+		assertTrue(result3);
+		assertTrue(result4);
+		assertTrue(result5);
+	}
+
+	private Boolean addToMap(MapOfMaps<String, String, String> mapOfMaps, AtomicBoolean run) {
+		for (; ; ) {
+			if (run.get())
+				break;
+		}
+
+		while (run.get()) {
+			addElement(mapOfMaps, "Resource", "Ball", UUID.randomUUID().toString());
+			addElement(mapOfMaps, "Resource", "Car", UUID.randomUUID().toString());
+			addElement(mapOfMaps, "Order", "StockOrder", UUID.randomUUID().toString());
+			addElement(mapOfMaps, "Order", "ToStock", UUID.randomUUID().toString());
+			addElement(mapOfMaps, "Order", "FromStock", UUID.randomUUID().toString());
+			addElement(mapOfMaps, "Activity", "FromStock", UUID.randomUUID().toString());
+			addElement(mapOfMaps, "Activity", "ToStock", UUID.randomUUID().toString());
+
+			mapOfMaps.removeElement("Resource", "Ball");
+			mapOfMaps.removeElement("Order", "ToStock");
+			mapOfMaps.removeElement("Activity", "ToStock");
+		}
+
+		return true;
+	}
+
+	private void addElement(MapOfMaps<String, String, String> mapOfMaps, String type, String subType, String id) {
+		logger.info("Adding " + type + " " + subType + " " + id);
+		mapOfMaps.addElement(type, subType, id);
+	}
+
+	private MapOfMaps<String, String, String> buildMapOfMaps() {
+		MapOfMaps<String, String, String> mapOfMaps = synchronizedMapOfMaps(new MapOfMaps<>(true));
+		mapOfMaps.addElement("Resource", "Ball", "yellow");
+		mapOfMaps.addElement("Resource", "Car", "car1");
+		mapOfMaps.addElement("Order", "StockOrder", "stockOrder1");
+		mapOfMaps.addElement("Order", "ToStock", "toStock1");
+		mapOfMaps.addElement("Order", "FromStock", "fromStock1");
+		mapOfMaps.addElement("Activity", "FromStock", "fromStock1");
+		mapOfMaps.addElement("Activity", "ToStock", "toStock1");
+
+		assertEquals("yellow", mapOfMaps.getElement("Resource", "Ball"));
+		assertNull(mapOfMaps.getMap("xxx"));
+		return mapOfMaps;
+	}
+}
diff --git a/li.strolch.utils/src/test/java/li/strolch/utils/collections/SynchronizedMapOfSetsTest.java b/li.strolch.utils/src/test/java/li/strolch/utils/collections/SynchronizedMapOfSetsTest.java
new file mode 100644
index 000000000..82f13de37
--- /dev/null
+++ b/li.strolch.utils/src/test/java/li/strolch/utils/collections/SynchronizedMapOfSetsTest.java
@@ -0,0 +1,160 @@
+package li.strolch.utils.collections;
+
+import static li.strolch.utils.collections.SynchronizedCollections.synchronizedMapOfSets;
+import static org.junit.Assert.*;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.UUID;
+import java.util.concurrent.*;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class SynchronizedMapOfSetsTest {
+
+	private static final Logger logger = LoggerFactory.getLogger(SynchronizedMapOfSetsTest.class);
+
+	private ExecutorService executorService;
+
+	@Before
+	public void before() {
+		this.executorService = Executors.newCachedThreadPool();
+	}
+
+	@Test
+	public void shouldForEach() throws ExecutionException, InterruptedException {
+
+		MapOfSets<String, String> mapOfSets = buildMapOfSets();
+		AtomicBoolean run = new AtomicBoolean(false);
+		Callable<Boolean> addTask = () -> addToMap(mapOfSets, run);
+
+		Callable<Boolean> iterateTask = () -> {
+			for (; ; ) {
+				if (run.get())
+					break;
+			}
+
+			while (run.get()) {
+				mapOfSets.forEach((s, list) -> list.forEach(s1 -> logger.info(s + " " + s1)));
+				mapOfSets.getSet("Resource").forEach(s1 -> logger.info("  " + s1));
+			}
+
+			return true;
+		};
+
+		runTest(addTask, iterateTask, run);
+	}
+
+	@Test
+	public void shouldIterate() throws ExecutionException, InterruptedException {
+
+		MapOfSets<String, String> mapOfSets = buildMapOfSets();
+		AtomicBoolean run = new AtomicBoolean(false);
+		Callable<Boolean> addTask = () -> addToMap(mapOfSets, run);
+		Callable<Boolean> iterateTask = () -> {
+			for (; ; ) {
+				if (run.get())
+					break;
+			}
+
+			while (run.get()) {
+				Set<String> types = mapOfSets.keySet();
+				for (String type : types) {
+					synchronized (mapOfSets) {
+						for (String id : mapOfSets.getSet(type)) {
+							logger.info(type + " " + id);
+						}
+					}
+				}
+
+				synchronized (mapOfSets) {
+					Set<String> resources = mapOfSets.getSet("Resource");
+					for (String value : resources) {
+						logger.info("Resource: value: " + value);
+					}
+				}
+			}
+
+			return true;
+		};
+
+		runTest(addTask, iterateTask, run);
+	}
+
+	private void runTest(Callable<Boolean> addTask, Callable<Boolean> iterateTask, AtomicBoolean run)
+			throws InterruptedException, ExecutionException {
+
+		Future<Boolean> task0 = this.executorService.submit(addTask);
+		Future<Boolean> task1 = this.executorService.submit(iterateTask);
+		Future<Boolean> task2 = this.executorService.submit(iterateTask);
+		Future<Boolean> task3 = this.executorService.submit(iterateTask);
+		Future<Boolean> task4 = this.executorService.submit(iterateTask);
+		Future<Boolean> task5 = this.executorService.submit(iterateTask);
+
+		run.set(true);
+		Thread.sleep(1000L);
+		run.set(false);
+
+		Boolean result0 = task0.get();
+		Boolean result1 = task1.get();
+		Boolean result2 = task2.get();
+		Boolean result3 = task3.get();
+		Boolean result4 = task4.get();
+		Boolean result5 = task5.get();
+
+		assertTrue(result0);
+		assertTrue(result1);
+		assertTrue(result2);
+		assertTrue(result3);
+		assertTrue(result4);
+		assertTrue(result5);
+	}
+
+	private Boolean addToMap(MapOfSets<String, String> mapOfSets, AtomicBoolean run) {
+		for (; ; ) {
+			if (run.get())
+				break;
+		}
+
+		while (run.get()) {
+			addElement(mapOfSets, "Resource", UUID.randomUUID().toString());
+			addElement(mapOfSets, "Resource", UUID.randomUUID().toString());
+			addElement(mapOfSets, "Order", UUID.randomUUID().toString());
+			addElement(mapOfSets, "Order", UUID.randomUUID().toString());
+			addElement(mapOfSets, "Order", UUID.randomUUID().toString());
+			addElement(mapOfSets, "Activity", UUID.randomUUID().toString());
+			addElement(mapOfSets, "Activity", UUID.randomUUID().toString());
+
+			mapOfSets.removeElement("Resource", "Ball");
+			mapOfSets.removeElement("Order", "ToStock");
+			mapOfSets.removeElement("Activity", "ToStock");
+		}
+
+		return true;
+	}
+
+	private void addElement(MapOfSets<String, String> mapOfSets, String type, String id) {
+		logger.info("Adding " + type + " " + id);
+		mapOfSets.addElement(type, id);
+	}
+
+	private MapOfSets<String, String> buildMapOfSets() {
+		MapOfSets<String, String> mapOfSets = synchronizedMapOfSets(new MapOfSets<>(true));
+		mapOfSets.addElement("Resource", "Ball");
+		mapOfSets.addElement("Resource", "Car");
+		mapOfSets.addElement("Order", "StockOrder");
+		mapOfSets.addElement("Order", "ToStock");
+		mapOfSets.addElement("Order", "FromStock");
+		mapOfSets.addElement("Activity", "FromStock");
+		mapOfSets.addElement("Activity", "ToStock");
+
+		assertEquals(new HashSet<>(Arrays.asList("Ball", "Car")), mapOfSets.getSet("Resource"));
+		assertNull(mapOfSets.getSet("xxx"));
+		return mapOfSets;
+	}
+}