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diff --git a/bin/uebung09/collection/SetFactory.class b/bin/uebung09/collection/SetFactory.class
index 4914357..4762368 100644
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diff --git a/bin/uebung09/collection/SingeltonSet$1.class b/bin/uebung09/collection/SingeltonSet$1.class
new file mode 100644
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diff --git a/bin/uebung09/collection/SingeltonSet.class b/bin/uebung09/collection/SingeltonSet.class
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diff --git a/src/test/uebung/uebung09/collection/SetTest.java b/src/test/uebung/uebung09/collection/SetTest.java
new file mode 100644
index 0000000..54a1547
--- /dev/null
+++ b/src/test/uebung/uebung09/collection/SetTest.java
@@ -0,0 +1,76 @@
+package test.uebung.uebung09.collection;
+
+import java.util.Iterator;
+
+import uebung09.collection.Set;
+import uebung09.collection.SetFactory;
+import java.util.NoSuchElementException;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class SetTest {
+
+    static String a = "test";
+    static String b = "test2";
+    static String c = "test3";
+
+
+    public static void main(String[] args) {
+    }
+
+    @Test
+    public void EmptySetTest(){
+
+        Set<String> test = SetFactory.create();
+
+        Iterator<String> i = test.iterator();
+
+        assertFalse(i.hasNext());
+        assertThrows(NoSuchElementException.class, i::next);
+        assertFalse(test.contains(a));
+        assertEquals(0,test.size());
+        assertTrue(test.isEmpty());
+    }
+
+    @Test
+    public void SingeltonSetTest(){
+
+        Set<String> test = SetFactory.create(a);
+
+        Iterator<String> i = test.iterator();
+
+        assertTrue(i.hasNext());
+        assertTrue(a == i.next());
+        assertFalse(i.hasNext());
+        assertThrows(NoSuchElementException.class, i::next);
+        assertTrue(test.contains(a));
+        assertEquals(1,test.size());
+        assertFalse(test.isEmpty());
+    }
+
+    @Test
+    public void BigSetTest() {
+
+        Set<String> test = SetFactory.create(a,b,c);
+
+        Iterator<String> i = test.iterator();
+
+        assertTrue(i.hasNext());
+        assertTrue(a == i.next());
+        assertTrue(i.hasNext());
+        assertTrue(a == i.next());
+        assertTrue(i.hasNext());
+        assertTrue(a == i.next());
+        assertFalse(i.hasNext());
+        assertThrows(NoSuchElementException.class, i::next);
+        assertTrue(test.contains(a));
+        assertEquals(1,test.size());
+        assertFalse(test.isEmpty());
+    }
+}
diff --git a/src/uebung09/collection/BigSet.java b/src/uebung09/collection/BigSet.java
new file mode 100644
index 0000000..7de961b
--- /dev/null
+++ b/src/uebung09/collection/BigSet.java
@@ -0,0 +1,94 @@
+package uebung09.collection;
+
+import java.util.Iterator;
+
+class BigSet<T> implements Set<T>{
+
+    private T item;
+    private Set<T> rest;
+
+    public BigSet(T item, Set<T> rest){
+        //TODO
+        this.item = item;
+        this.rest = rest;
+    }
+
+    @Override
+    public Iterator<T> iterator() {
+        return new Iterator<T>() {
+
+            private boolean returned = false;
+
+            private Iterator<T> restI = rest.iterator();
+            
+            @Override
+            public boolean hasNext() {
+                return restI.hasNext();
+            }
+
+            @Override
+            public T next() {
+                if (!returned) {
+                    returned = true;
+                    return item;
+                } else {
+                    return restI.next();
+                }
+            }
+        };
+    }
+
+    @Override
+    public int size() {
+        int count = 1;
+        count += rest.size();
+
+        return count;
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return false;
+    }
+
+    @Override
+    public boolean contains(Object el) {
+        if(el == item) {
+            return true;
+        } else {
+            return rest.contains(el);
+        }
+    }
+
+    @Override
+    public Set<T> union(Set<T> other) {
+        if (other == EmptySet.getInstance()) {
+            return this;
+        } else if (other instanceof SingeltonSet<T> && !contains(other.iterator().next())) {
+            return new BigSet<T>(other.iterator().next(), this);
+        } else {
+            return new BigSet<T>(item, rest.union(other));
+        }
+    }
+
+    @Override
+    public Set<T> add(T element) {
+        if (contains(element)) {
+            return this;
+        } else {
+            return new BigSet<T>(element, this);
+        }
+    }
+
+    @Override
+    public Set<T> intersection(Set<T> other) {
+        // TODO Auto-generated method stub
+        throw new UnsupportedOperationException("Unimplemented method 'intersection'");
+    }
+
+    @Override
+    public boolean subsetOf(Set<?> other) {
+        // TODO Auto-generated method stub
+        throw new UnsupportedOperationException("Unimplemented method 'subsetOf'");
+    }
+}
diff --git a/src/uebung09/collection/EmptySet.java b/src/uebung09/collection/EmptySet.java
new file mode 100644
index 0000000..55aa694
--- /dev/null
+++ b/src/uebung09/collection/EmptySet.java
@@ -0,0 +1,71 @@
+package uebung09.collection;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+class EmptySet<T> implements Set<T> {
+
+    private static EmptySet<?> INSTANCE;
+
+    private EmptySet() {}
+
+    @SuppressWarnings("unchecked")
+    public static <T> EmptySet<T> getInstance() {
+        if (INSTANCE == null) {
+            INSTANCE = new EmptySet<>();
+        }
+        return (EmptySet<T>) INSTANCE;
+    }
+
+    @Override
+    public Iterator<T> iterator() {
+        return new Iterator<T>() {
+            
+            @Override
+            public boolean hasNext() {
+                return false;
+            }
+
+            @Override
+            public T next() {
+                throw new NoSuchElementException();
+            }
+        };
+    }
+
+    @Override
+    public int size() {
+        return 0;
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return true;
+    }
+
+    @Override
+    public boolean contains(Object el) {
+        return false;
+    }
+
+    @Override
+    public Set<T> union(Set<T> other) {
+        return other;
+    }
+
+    @Override
+    public Set<T> add(T element) {
+        return new SingeltonSet<T>(element);
+    }
+
+    @Override
+    public Set<T> intersection(Set<T> other) {
+        return other;
+    }
+
+    @Override
+    public boolean subsetOf(Set<?> other) {
+        return true;
+    }
+
+}
diff --git a/src/uebung09/collection/Set.java b/src/uebung09/collection/Set.java
index 00171e8..d982b02 100644
--- a/src/uebung09/collection/Set.java
+++ b/src/uebung09/collection/Set.java
@@ -38,10 +38,10 @@ public interface Set<E> extends Iterable<E> {
     /**
      * returns the set resulting from adding the specified element to this set.
      *
-     * @param element an element (must not be null)
+     * @param elem an element (must not be null)
      * @return the set resulting from adding the specified element to this set.
      */
-    Set<E> add(E element);
+    Set<E> add(E elem);
 
     /**
      * Returns the intersection of this set and the specified set.
diff --git a/src/uebung09/collection/SetFactory.java b/src/uebung09/collection/SetFactory.java
index f8cfeb3..fb96697 100644
--- a/src/uebung09/collection/SetFactory.java
+++ b/src/uebung09/collection/SetFactory.java
@@ -10,9 +10,8 @@ public class SetFactory {
      * @param <T> the element type of the returned set.
      * @return the empty set.
      */
-    static <T> Set<T> create() {
-        // TODO implement
-        return null;
+    public static <T> Set<T> create() {
+        return EmptySet.getInstance();
     }
 
     /**
@@ -22,9 +21,8 @@ public class SetFactory {
      * @param <T>     the element type of the returned set.
      * @return the singleton set containing the specified element.
      */
-    static <T> Set<T> create(T element) {
-        // TODO implement
-        return null;
+    public static <T> Set<T> create(T element) {
+        return new SingeltonSet<T>(element);
     }
 
     /**
@@ -34,8 +32,14 @@ public class SetFactory {
      * @param <T>   the element type of the returned set.
      * @return a set containing the specified elements.
      */
-    static <T> Set<T> create(T... elems) {
-        // TODO implement
-        return null;
+    public static <T> Set<T> create(T... elems) {
+        // BigSet<T> rtn = new BigSet<T>(elems[1], new SingeltonSet<>(elems[1]));
+        Set<T> set = EmptySet.getInstance();
+
+        for(T elem : elems) {
+            set = set.add(elem);
+        }
+
+        return set;
     }
 }
diff --git a/src/uebung09/collection/SingeltonSet.java b/src/uebung09/collection/SingeltonSet.java
new file mode 100644
index 0000000..afa3870
--- /dev/null
+++ b/src/uebung09/collection/SingeltonSet.java
@@ -0,0 +1,77 @@
+package uebung09.collection;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+class SingeltonSet<T> implements Set<T> {
+
+    private T item;
+
+    public SingeltonSet(T item) {
+        this.item = item;
+    }
+
+    @Override
+    public Iterator<T> iterator() {
+        return new Iterator<T>() {
+
+            boolean returned = false;
+
+            @Override
+            public boolean hasNext() {
+                return !returned;
+            }
+
+            @Override
+            public T next() {
+                if (!returned) {
+                    returned = true;
+                    return item;
+                } else {
+                    throw new NoSuchElementException();
+                }
+            }
+        };
+    }
+
+    @Override
+    public int size() {
+        return 1;
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return false;
+    }
+
+    @Override
+    public boolean contains(Object el) {
+        return el == item;
+    }
+
+    @Override
+    public Set<T> union(Set<T> other) {
+        //TODO
+        return null;
+    }
+
+    @Override
+    public Set<T> add(T element) {
+        if (element == item) {
+            return this;
+        } else {
+            return new BigSet<T>(item, new SingeltonSet<T>(element));
+        }
+    }
+
+    @Override
+    public Set<T> intersection(Set<T> other) {
+        // TODO Auto-generated method stub
+        throw new UnsupportedOperationException("Unimplemented method 'intersection'");
+    }
+
+    @Override
+    public boolean subsetOf(Set<?> other) {
+        throw new UnsupportedOperationException();
+    }
+}