diff --git a/src/main/java/de/joethei/hs/java2/praktikum/praktikum1/GrosseZahl.java b/src/main/java/de/joethei/hs/java2/praktikum/praktikum1/GrosseZahl.java
index 79dc73f..ba94468 100644
--- a/src/main/java/de/joethei/hs/java2/praktikum/praktikum1/GrosseZahl.java
+++ b/src/main/java/de/joethei/hs/java2/praktikum/praktikum1/GrosseZahl.java
@@ -17,7 +17,7 @@ public class GrosseZahl {
                 zahl[w] = Integer.parseInt(String.valueOf(d.charAt(w)));
             }
         } else {
-            System.out.println("Incorrect Input!");
+            throw new IllegalArgumentException("falscher Input");
         }
     }
 
@@ -118,11 +118,11 @@ public class GrosseZahl {
     }
 
 
-    private int length() {
+    public int length() {
         return zahl.length;
     }
 
-    private int numberAt(int i) {
+    public int numberAt(int i) {
         return zahl[i];
     }
 
diff --git a/src/main/java/de/joethei/hs/java2/vorlesungen/binaryTree/Node.java b/src/main/java/de/joethei/hs/java2/vorlesungen/binaryTree/Node.java
index b74dcd7..0832ef7 100644
--- a/src/main/java/de/joethei/hs/java2/vorlesungen/binaryTree/Node.java
+++ b/src/main/java/de/joethei/hs/java2/vorlesungen/binaryTree/Node.java
@@ -10,9 +10,6 @@ public class Node<T> {
 
     private Logger logger = Logger.getLogger(getClass().getName());
 
-    public Node() {
-    }
-
     public Node(T value) {
         this.value = value;
     }
@@ -35,11 +32,6 @@ public class Node<T> {
         return right;
     }
 
-    @Override
-    public String toString() {
-        return super.toString();
-    }
-
     @Override
     public boolean equals(Object obj) {
         if (obj instanceof Node) {
diff --git a/src/main/java/de/joethei/hs/java2/vorlesungen/binaryTree/Tree.java b/src/main/java/de/joethei/hs/java2/vorlesungen/binaryTree/Tree.java
index 95d6b6d..a594a5e 100644
--- a/src/main/java/de/joethei/hs/java2/vorlesungen/binaryTree/Tree.java
+++ b/src/main/java/de/joethei/hs/java2/vorlesungen/binaryTree/Tree.java
@@ -12,9 +12,4 @@ public class Tree<T> {
         return root;
     }
 
-    @Override
-    public boolean equals(Object obj) {
-        if(obj instanceof Tree) return root.equals(obj);
-        return false;
-    }
 }
\ No newline at end of file
diff --git a/src/test/java/de/joethei/hs/java2/tests/CharCollectionTest.java b/src/test/java/de/joethei/hs/java2/tests/CharCollectionTest.java
index b8f47c8..39aa249 100644
--- a/src/test/java/de/joethei/hs/java2/tests/CharCollectionTest.java
+++ b/src/test/java/de/joethei/hs/java2/tests/CharCollectionTest.java
@@ -49,6 +49,7 @@ public class CharCollectionTest {
     @Test
     public void equals() {
         assertEquals(new CharCollection("llo"), new CharCollection("lol"));
+        assertNotEquals(new CharCollection("Hallo"), "Hallo");
     }
 
     @Test
diff --git a/src/test/java/de/joethei/hs/java2/tests/GrosseZahlTest.java b/src/test/java/de/joethei/hs/java2/tests/GrosseZahlTest.java
index 53b7a4f..6c36b19 100644
--- a/src/test/java/de/joethei/hs/java2/tests/GrosseZahlTest.java
+++ b/src/test/java/de/joethei/hs/java2/tests/GrosseZahlTest.java
@@ -14,6 +14,18 @@ public class GrosseZahlTest {
         assertNotEquals(new GrosseZahl(14), 14);
     }
 
+    @Test
+    public void length() {
+        assertEquals(4, new GrosseZahl("1234").length());
+        assertNotEquals(5, new GrosseZahl(1234).length());
+    }
+
+    @Test
+    public void numberAt() {
+        assertEquals(5, new GrosseZahl("125").numberAt(2));
+        assertNotEquals(5, new GrosseZahl(125).numberAt(1));
+    }
+
 
     @Test
     public void add() {
@@ -33,6 +45,7 @@ public class GrosseZahlTest {
         assertNotEquals(new GrosseZahl(43), new GrosseZahl(100).sub(new GrosseZahl(58)));
         assertEquals(new GrosseZahl(100), new GrosseZahl(150).sub(new GrosseZahl(50)));
         assertEquals(new GrosseZahl(0), new GrosseZahl(10).sub(new GrosseZahl("10")));
+        assertEquals(new GrosseZahl(0), new GrosseZahl(10).sub(new GrosseZahl(15)));
     }
 
     @Test
@@ -64,4 +77,9 @@ public class GrosseZahlTest {
         assertNotEquals(new GrosseZahl(2), new GrosseZahl("7").ggT(new GrosseZahl(13)));
     }
 
+    @Test(expected = IllegalArgumentException.class)
+    public void wrongInput() {
+        new GrosseZahl("42B");
+    }
+
 }
\ No newline at end of file
diff --git a/src/test/java/de/joethei/hs/java2/tests/VorlesungsTest.java b/src/test/java/de/joethei/hs/java2/tests/VorlesungsTest.java
index e2a159b..16397d2 100644
--- a/src/test/java/de/joethei/hs/java2/tests/VorlesungsTest.java
+++ b/src/test/java/de/joethei/hs/java2/tests/VorlesungsTest.java
@@ -10,6 +10,8 @@ import java.util.Set;
 import java.util.TreeSet;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertTrue;
 
 
 public class VorlesungsTest {
@@ -29,5 +31,8 @@ public class VorlesungsTest {
         assertEquals(Integer.valueOf(16), tree.getRoot().getRight().getValue());
 
         assertEquals(tree.getRoot(), node);
+
+
+        assertNotEquals(node, "HalloWelt");
     }
 }
\ No newline at end of file