final Version

pp.A4-HandOverHandLocking/src/main/java/pp/Main.java

@@ -13,7 +13,8 @@ public class Main {
             if (sum != expected) {
                 System.out.println("Fehler in "
                         + Thread.currentThread().getName() + ": " + sum);
-            }
+            }else
+            	System.out.println("Kein Fehler in " + Thread.currentThread().getName() + ": " + sum);
         };
     }
 

pp.A4-HandOverHandLocking/src/main/java/pp/SimplifiedList.java

@@ -7,6 +7,7 @@ public interface SimplifiedList<T> {
      *
      * @param index index of the element to return
      * @return the element at the specified position in this list
+     * @throws Exception 
      */
     public T get(int index);
 
@@ -28,6 +29,7 @@ public interface SimplifiedList<T> {
      * @param index   index of the element to replace
      * @param element element to be stored at the specified position
      * @return the element previously at the specified position
+     * @throws Exception 
      */
     public T set(int index, T element);
 

pp.A4-HandOverHandLocking/src/main/java/pp/ThreadsafeSimplifiedList.java

@@ -29,13 +29,14 @@ public class ThreadsafeSimplifiedList<T>
      * @return the element at the specified position in this list
      */
     @Override
-  public T get(int index) {
+    public T get(int index){
         this.listLock.lock();
-    var ptr = this.head;
+        if (this.head == null) {
-    if (ptr == null) {
         	this.listLock.unlock();
-      throw new IndexOutOfBoundsException(index + " out of bounds (empty list)");
+        	throw new IndexOutOfBoundsException("The list is empty");    
         }
+        
+        var ptr = this.head;
         ptr.nodeLock.lock();
         this.listLock.unlock();
         for (var i = 0; i < index; i++) {
@@ -45,16 +46,12 @@ public class ThreadsafeSimplifiedList<T>
                 ptr = ptr.next;
                 savePtr.nodeLock.unlock();
             } else {
-        ptr.nodeLock.unlock();
                 throw new IndexOutOfBoundsException(index + " out of bounds");            
             }
         }
         
-    try {
+        try {return delay(ptr.element);} 
-      return delay(ptr.element);
+        finally { ptr.nodeLock.unlock();}
-    } finally {
-      ptr.nodeLock.unlock();
-    }
     }
 
     /**
@@ -99,11 +96,11 @@ public class ThreadsafeSimplifiedList<T>
     @Override
     public T set(int index, T element) {
         this.listLock.lock();
-    var ptr = this.head;
+        if (this.head == null) {
-    if (ptr == null) {
         	this.listLock.unlock();
-      throw new IndexOutOfBoundsException(index + " out of bounds (empty list)");
+        	throw new IndexOutOfBoundsException("The list is empty");    
         }
+        var ptr = this.head;
         ptr.nodeLock.lock();
         this.listLock.unlock();
         for (var i = 0; i < index; i++) {
@@ -112,16 +109,13 @@ public class ThreadsafeSimplifiedList<T>
                 var savePtr = ptr;
                 ptr = ptr.next;
                 savePtr.nodeLock.unlock();
-      } else {
+            } else 
-        ptr.nodeLock.unlock();
                 throw new IndexOutOfBoundsException(index + " out of bounds");           
-      }
-    }
            
+        }
         try {
-      T old = ptr.element;
             ptr.element = element;
-      return old;
+            return element;
         } finally {
             ptr.nodeLock.unlock();
         }
@@ -135,10 +129,7 @@ public class ThreadsafeSimplifiedList<T>
     @Override
     public boolean isEmpty() {
         this.listLock.lock();
-    try {
+        try { return this.head == null; } 
-      return this.head == null;
+        finally { this.listLock.unlock();}
-    } finally {
-      this.listLock.unlock();
-    }
     }
 }