diff --git a/SimpleActivityStack/.classpath b/SimpleActivityStack/.classpath
new file mode 100644
index 0000000..be55723
--- /dev/null
+++ b/SimpleActivityStack/.classpath
@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8"/>
+	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="con" path="org.eclipse.jdt.junit.JUNIT_CONTAINER/5"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>
diff --git a/SimpleActivityStack/.project b/SimpleActivityStack/.project
new file mode 100644
index 0000000..19501f2
--- /dev/null
+++ b/SimpleActivityStack/.project
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>SimpleActivityStack</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>
diff --git a/SimpleActivityStack/src/solution/SimpleActivityStack.java b/SimpleActivityStack/src/solution/SimpleActivityStack.java
new file mode 100644
index 0000000..a183c0c
--- /dev/null
+++ b/SimpleActivityStack/src/solution/SimpleActivityStack.java
@@ -0,0 +1,38 @@
+package solution;
+
+import testat.SimpleActivity;
+
+public class SimpleActivityStack extends SimpleStack<SimpleActivity> {
+
+	@Override
+	public int push(SimpleActivity activity) {
+		if (size() > 0) {
+			super.get(size() - 1).passivate();
+		}
+		activity.activate();
+		return super.push(activity);
+	}
+
+	@Override
+	public SimpleActivity pop() {
+		SimpleActivity activity = super.pop();
+		if (activity != null) {
+			activity.passivate();
+			activity.destroy();
+			if (size() > 0) {
+				super.get(size() - 1).activate();
+			}
+		}
+		return activity;
+	}
+
+	@Override
+	public SimpleActivity remove(int i) {
+		if (i == super.size() - 1) {
+			return this.pop();
+		}
+		super.get(i).destroy();
+		return super.remove(i);
+	}
+
+}
diff --git a/SimpleActivityStack/src/solution/SimpleActivityStackTest.java b/SimpleActivityStack/src/solution/SimpleActivityStackTest.java
new file mode 100644
index 0000000..73d60b8
--- /dev/null
+++ b/SimpleActivityStack/src/solution/SimpleActivityStackTest.java
@@ -0,0 +1,14 @@
+package solution;
+
+import testat.ASimpleActivityStackTest;
+import testat.ISimpleStack;
+import testat.SimpleActivity;
+
+public class SimpleActivityStackTest extends ASimpleActivityStackTest {
+
+	@Override
+	protected ISimpleStack<SimpleActivity> getInstance() {
+		return new SimpleActivityStack();
+	}
+
+}
diff --git a/SimpleActivityStack/src/solution/SimpleStack.java b/SimpleActivityStack/src/solution/SimpleStack.java
new file mode 100644
index 0000000..3ed4186
--- /dev/null
+++ b/SimpleActivityStack/src/solution/SimpleStack.java
@@ -0,0 +1,64 @@
+package solution;
+
+import java.util.LinkedList;
+import java.util.List;
+
+import testat.IAction;
+import testat.ISimpleStack;
+
+public class SimpleStack<T> implements ISimpleStack<T> {
+
+	private List<T> list;
+
+	public SimpleStack() {
+		super();
+		list = new LinkedList<T>();
+	}
+
+	@Override
+	public int push(T t) {
+		if (t != null) {
+			if (list.contains(t)) {
+				list.remove(t);
+			}
+			list.add(t);
+			return list.size();
+		}
+		return 0;
+	}
+
+	@Override
+	public T pop() {
+		if (list.size() == 0) {
+			return null;
+		}
+		return list.remove(list.size() - 1);
+	}
+
+	@Override
+	public T remove(int i) {
+		return list.remove(i);
+	}
+
+	@Override
+	public int size() {
+		return list.size();
+	}
+
+	@Override
+	public boolean contains(Object o) {
+		return list.contains(o);
+	}
+
+	@Override
+	public T get(int i) {
+		return list.get(i);
+	}
+
+	@Override
+	public void forAll(IAction<T> action) {
+		if (action != null) {
+			list.forEach(t -> action.execute(t));
+		}
+	}
+}
diff --git a/SimpleActivityStack/src/solution/SimpleStackTest.java b/SimpleActivityStack/src/solution/SimpleStackTest.java
new file mode 100644
index 0000000..84e2a48
--- /dev/null
+++ b/SimpleActivityStack/src/solution/SimpleStackTest.java
@@ -0,0 +1,13 @@
+package solution;
+
+import testat.ASimpleStackTest;
+import testat.ISimpleStack;
+
+public class SimpleStackTest extends ASimpleStackTest {
+
+	@Override
+	protected ISimpleStack<String> getInstance() {
+		return new SimpleStack<>();
+	}
+
+}