diff --git a/pom.xml b/pom.xml
index f2f2be0..1464b97 100644
--- a/pom.xml
+++ b/pom.xml
@@ -54,6 +54,33 @@
             <version>4.12.1</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <version>2.9.0</version>
+        </dependency>
+        <dependency>
+            <groupId>org.powermock</groupId>
+            <artifactId>powermock-api-mockito-common</artifactId>
+            <version>1.7.3</version>
+        </dependency>
+        <dependency>
+            <groupId>org.powermock</groupId>
+            <artifactId>powermock-module-junit4</artifactId>
+            <version>1.7.3</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.powermock</groupId>
+            <artifactId>powermock-api-mockito2</artifactId>
+            <version>1.7.3</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>log4j</groupId>
+            <artifactId>log4j</artifactId>
+            <version>1.2.17</version>
+        </dependency>
     </dependencies>
 
 </project>
\ No newline at end of file
diff --git a/src/main/java/de/joethei/hs/java2/Klausur.java b/src/main/java/de/joethei/hs/java2/Klausur.java
new file mode 100644
index 0000000..a4913e7
--- /dev/null
+++ b/src/main/java/de/joethei/hs/java2/Klausur.java
@@ -0,0 +1,12 @@
+package de.joethei.hs.java2;
+
+public class Klausur {
+
+    public boolean istPalindrom(String satz) {
+        if(satz.length() <= 1) return true;
+        if(satz.charAt(0) == satz.charAt(satz.length()-1)) {
+            return istPalindrom(satz.substring(1, satz.length()-1));
+        }
+        return false;
+    }
+}
\ No newline at end of file
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 8dd116c..98f21d7 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
@@ -160,6 +160,10 @@ public class GrosseZahl {
 
     @Override
     public int hashCode() {
-        return super.hashCode();
+        int result = 0;
+        for(int i : zahl) {
+            result += i;
+        }
+        return result * zahl.length;
     }
 }
diff --git a/src/main/java/de/joethei/hs/java2/praktikum/praktikum2/CharCollection.java b/src/main/java/de/joethei/hs/java2/praktikum/praktikum2/CharCollection.java
index 00d1699..c6f8e63 100644
--- a/src/main/java/de/joethei/hs/java2/praktikum/praktikum2/CharCollection.java
+++ b/src/main/java/de/joethei/hs/java2/praktikum/praktikum2/CharCollection.java
@@ -106,6 +106,11 @@ public class CharCollection implements Cloneable{
 
     @Override
     public int hashCode() {
-        return super.hashCode();
+        int result = 0;
+        for(char c : list) {
+            result += c;
+        }
+
+        return result * list.size();
     }
 }
\ No newline at end of file
diff --git a/src/main/java/de/joethei/hs/java2/praktikum/praktikum4/ClientRunnable.java b/src/main/java/de/joethei/hs/java2/praktikum/praktikum4/ClientRunnable.java
index b2ef683..e7bbf68 100644
--- a/src/main/java/de/joethei/hs/java2/praktikum/praktikum4/ClientRunnable.java
+++ b/src/main/java/de/joethei/hs/java2/praktikum/praktikum4/ClientRunnable.java
@@ -15,7 +15,7 @@ public class ClientRunnable implements Runnable{
         try {
             bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
         } catch (IOException e) {
-            e.printStackTrace();
+            KlausurenServer.getLogger().fatal(this, e.getCause());
         }
     }
 
@@ -35,7 +35,7 @@ public class ClientRunnable implements Runnable{
             Thread.currentThread().interrupt();
 
         } catch (IOException e) {
-            e.printStackTrace();
+            KlausurenServer.getLogger().error(this, e.getCause());
         }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/de/joethei/hs/java2/praktikum/praktikum4/KlausurenServer.java b/src/main/java/de/joethei/hs/java2/praktikum/praktikum4/KlausurenServer.java
index f1eed2c..c9cb3b8 100644
--- a/src/main/java/de/joethei/hs/java2/praktikum/praktikum4/KlausurenServer.java
+++ b/src/main/java/de/joethei/hs/java2/praktikum/praktikum4/KlausurenServer.java
@@ -1,10 +1,11 @@
 package de.joethei.hs.java2.praktikum.praktikum4;
 
+import org.apache.log4j.Logger;
+
 import java.io.*;
 import java.net.ServerSocket;
 import java.util.*;
 import java.util.concurrent.*;
-import java.util.logging.Logger;
 
 public class KlausurenServer {
 
@@ -112,7 +113,7 @@ public class KlausurenServer {
                 logger.info("server shutdown");
                 Thread.currentThread().interrupt();
             } catch (IOException e) {
-                logger.throwing("KlausurenServer", "Constructor", e.getCause());
+                logger.error(this, e.getCause());
             }
 
         };
@@ -125,7 +126,7 @@ public class KlausurenServer {
         try {
             fileReader = new FileReader(Objects.requireNonNull(getClass().getClassLoader().getResource("praktikum4/data.txt")).getFile());
         } catch (FileNotFoundException e) {
-            logger.throwing("KlausurenServer", "load", e.getCause());
+            logger.error(this, e.getCause());
         }
         try (BufferedReader br = new BufferedReader(Objects.requireNonNull(fileReader))) {
             for (String line = br.readLine(); line != null; line = br.readLine()) {
@@ -137,7 +138,7 @@ public class KlausurenServer {
                 data.put(array[0], set);
             }
         } catch (IOException e) {
-            logger.throwing("KlausurenServer", "load", e.getCause());
+            logger.error(this, e.getCause());
         }
     }
 
@@ -157,7 +158,7 @@ public class KlausurenServer {
 
             }
         } catch (IOException e) {
-            logger.throwing("KlausurenServer", "save", e.getCause());
+            logger.error(this, e.getCause());
         } finally {
             assert printWriter != null;
             printWriter.close();
diff --git a/src/main/resources/log4j.properties b/src/main/resources/log4j.properties
new file mode 100644
index 0000000..393e087
--- /dev/null
+++ b/src/main/resources/log4j.properties
@@ -0,0 +1,8 @@
+# Root logger option
+log4j.rootLogger=INFO, stdout
+
+# Direct log messages to stdout
+log4j.appender.stdout=org.apache.log4j.ConsoleAppender
+log4j.appender.stdout.Target=System.out
+log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
+log4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n
\ 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 b26dfb6..30c59f4 100644
--- a/src/test/java/de/joethei/hs/java2/tests/CharCollectionTest.java
+++ b/src/test/java/de/joethei/hs/java2/tests/CharCollectionTest.java
@@ -62,4 +62,9 @@ public class CharCollectionTest {
         assertTrue(new CharCollection("Hallo").isSubset(new CharCollection("Hao")));
     }
 
+    @Test
+    public void hashCodeTest() {
+        assertEquals(new CharCollection("HalloWorld").hashCode(), new CharCollection("HalloWorld").hashCode());
+    }
+
  }
\ No newline at end of file
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 85563d3..111a252 100644
--- a/src/test/java/de/joethei/hs/java2/tests/GrosseZahlTest.java
+++ b/src/test/java/de/joethei/hs/java2/tests/GrosseZahlTest.java
@@ -83,4 +83,9 @@ public class GrosseZahlTest {
         new GrosseZahl("42/");
     }
 
+    @Test
+    public void hashCodeTest() {
+        assertEquals(new GrosseZahl(42).hashCode(), new GrosseZahl("42").hashCode());
+    }
+
 }
\ No newline at end of file
diff --git a/src/test/java/de/joethei/hs/java2/tests/KlausurTest.java b/src/test/java/de/joethei/hs/java2/tests/KlausurTest.java
new file mode 100644
index 0000000..5346517
--- /dev/null
+++ b/src/test/java/de/joethei/hs/java2/tests/KlausurTest.java
@@ -0,0 +1,20 @@
+package de.joethei.hs.java2.tests;
+
+import de.joethei.hs.java2.Klausur;
+import org.junit.Test;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class KlausurTest {
+
+    @Test
+    public void istPalindrom() {
+        Klausur klausur = new Klausur();
+        assertTrue(klausur.istPalindrom("ABBA"));
+        assertTrue(klausur.istPalindrom("lagerregal"));
+        assertTrue(klausur.istPalindrom("a"));
+        assertTrue(klausur.istPalindrom(""));
+        assertFalse(klausur.istPalindrom("Hallo Welt"));
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/de/joethei/hs/java2/tests/KlausurenServerTest3.java b/src/test/java/de/joethei/hs/java2/tests/KlausurenServerTest3.java
new file mode 100644
index 0000000..42e4458
--- /dev/null
+++ b/src/test/java/de/joethei/hs/java2/tests/KlausurenServerTest3.java
@@ -0,0 +1,50 @@
+package de.joethei.hs.java2.tests;
+
+import de.joethei.hs.java2.praktikum.praktikum4.KlausurenServer;
+import org.apache.log4j.AppenderSkeleton;
+import org.apache.log4j.Logger;
+import org.apache.log4j.spi.LoggingEvent;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Captor;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.powermock.api.mockito.PowerMockito;
+import org.powermock.modules.junit4.PowerMockRunner;
+
+import java.io.*;
+import java.net.Socket;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.verify;
+
+@RunWith(PowerMockRunner.class)
+public class KlausurenServerTest3 {
+
+    @InjectMocks
+    private KlausurenServer klausurenServer = new KlausurenServer(6770);
+
+    @Mock
+    private Socket socket;
+    @Mock
+    AppenderSkeleton appender;
+    @Captor
+    ArgumentCaptor<LoggingEvent> logCaptor;
+
+    @Test(expected = IOException.class)
+    public void ioException() throws Exception {
+        PowerMockito.whenNew(OutputStreamWriter.class).withArguments(new Socket().getOutputStream()).thenAnswer(invocationOnMock -> {
+            throw new IOException("TestCase");
+        });
+        Logger.getLogger("KlausurenServer").addAppender(appender);
+
+        verify(appender).doAppend(logCaptor.capture());
+
+        assertEquals("test", "test", logCaptor.getValue().getRenderedMessage());
+
+
+        KlausurenServer klausurenServer = new KlausurenServer(6770);
+
+    }
+}
\ No newline at end of file