diff --git a/pom.xml b/pom.xml
new file mode 100644
index 0000000..d3ca212
--- /dev/null
+++ b/pom.xml
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>pp.hsma</groupId>
+    <artifactId>pp.A4</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+</project>
diff --git a/src/main/java/io/dama/ffi/hoh/Main.java b/src/main/java/io/dama/ffi/hoh/Main.java
new file mode 100644
index 0000000..82db479
--- /dev/null
+++ b/src/main/java/io/dama/ffi/hoh/Main.java
@@ -0,0 +1,41 @@
+package io.dama.ffi.hoh;
+
+public class Main {
+    static SimplifiedList<Integer> list;
+
+    static Runnable sliceSum(int start, int end, int expected) {
+        return () -> {
+            var sum = 0;
+            for (var i = start; i < end; i++) {
+                sum += list.get(i);
+            }
+            if (sum != expected) {
+                System.out.println("Fehler in "
+                        + Thread.currentThread().getName() + ": " + sum);
+            }
+        };
+    }
+
+    public static void main(String... args) throws InterruptedException {
+        list = new ThreadsafeSimplifiedList<>();
+        for (int i = 0; i < 5000; i++) {
+            list.add(i);
+        }
+        var thread0 = new Thread(sliceSum(0, 1250, 780625));
+        var thread1 = new Thread(sliceSum(1250, 2500, 2343125));
+        var thread2 = new Thread(sliceSum(2500, 3750, 3905625));
+        var thread3 = new Thread(sliceSum(3750, 5000, 5468125));
+        var start = System.currentTimeMillis();
+        thread0.start();
+        thread1.start();
+        thread2.start();
+        thread3.start();
+        thread0.join();
+        thread1.join();
+        thread2.join();
+        thread3.join();
+        System.out.printf("%s: %d ms\n", list.getClass().toString(),
+                System.currentTimeMillis() - start);
+    }
+
+}
diff --git a/src/main/java/io/dama/ffi/hoh/SimplifiedList.java b/src/main/java/io/dama/ffi/hoh/SimplifiedList.java
new file mode 100644
index 0000000..5fc52c3
--- /dev/null
+++ b/src/main/java/io/dama/ffi/hoh/SimplifiedList.java
@@ -0,0 +1,56 @@
+package io.dama.ffi.hoh;
+
+public interface SimplifiedList<T> {
+
+    /**
+     * Returns the element at the specified position in this list.
+     *
+     * @param index index of the element to return
+     * @return the element at the specified position in this list
+     */
+    public T get(int index);
+
+    /**
+     * Appends the specified element to the end of this list. There are no
+     * limitations on what elements may be added to this list.
+     * 
+     * @param element element to be appended to this list
+     * @return true
+     * @see java.util.Collection#add(Object)
+     *
+     */
+    public boolean add(T element);
+
+    /**
+     * Replaces the element at the specified position in this list with the
+     * specified element.
+     * 
+     * @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
+     */
+    public T set(int index, T element);
+
+    /**
+     * Returns true if this list contains no elements.
+     * 
+     * @return true if this list contains no elements
+     */
+    public boolean isEmpty();
+
+    /**
+     * delayed passing through of parameter
+     * 
+     * @param element element to pass through
+     * @return passed though element
+     *
+     */
+    public default T delay(T element) {
+        try {
+            Thread.sleep(10);
+        } catch (InterruptedException ex) {
+            Thread.currentThread().interrupt();
+        }
+        return element;
+    }
+}
diff --git a/src/main/java/io/dama/ffi/hoh/ThreadsafeSimplifiedList.java b/src/main/java/io/dama/ffi/hoh/ThreadsafeSimplifiedList.java
new file mode 100644
index 0000000..bbc53aa
--- /dev/null
+++ b/src/main/java/io/dama/ffi/hoh/ThreadsafeSimplifiedList.java
@@ -0,0 +1,90 @@
+package io.dama.ffi.hoh;
+
+public class ThreadsafeSimplifiedList<T> implements SimplifiedList<T> {
+    private Node<T> first;
+
+    private class Node<U> {
+        private U element;
+        private Node<U> prev;
+        private Node<U> next;
+
+        private Node(U element, Node<U> prev, Node<U> next) {
+            super();
+            this.element = element;
+            this.prev = prev;
+            this.next = next;
+        }
+    }
+
+    public ThreadsafeSimplifiedList() {
+        super();
+        this.first = null;
+    }
+
+    /**
+     * Returns the element at the specified position in this list.
+     *
+     * @param index index of the element to return
+     * @return the element at the specified position in this list
+     */
+    @Override
+    public synchronized T get(int index) {
+        var ptr = this.first;
+        for (var j = 0; j < index; j++) {
+            ptr = ptr.next;
+        }
+        return delay(ptr.element);
+    }
+
+    /**
+     * Appends the specified element to the end of this list. There are no
+     * limitations on what elements may be added to this list.
+     * 
+     * @param element element to be appended to this list
+     * @return true
+     * @see java.util.Collection#add(Object)
+     *
+     */
+    @Override
+    public synchronized boolean add(T element) {
+        if (this.first != null) {
+            var ptr = this.first;
+            while (ptr.next != null) {
+                ptr = ptr.next;
+            }
+            ptr.next = new Node<>(element, ptr, null);
+        } else {
+            this.first = new Node<>(element, null, null);
+        }
+        return true;
+    }
+
+    /**
+     * Replaces the element at the specified position in this list with the
+     * specified element.
+     * 
+     * @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
+     */
+    @Override
+    public synchronized T set(int index, T element) {
+        var ptr = this.first;
+        for (var j = 0; j < index; j++) {
+            ptr = ptr.next;
+        }
+        var prevElement = ptr.element;
+        ptr.element = element;
+        return prevElement;
+    }
+
+    /**
+     * Returns true if this list contains no elements.
+     * 
+     * @return true if this list contains no elements
+     */
+    @Override
+    public synchronized boolean isEmpty() {
+        return this.first == null;
+    }
+}