Add a class for storing sorted items

app/src/main/java/ch/nuth/zhaw/exbox/MySortedList.java

@@ -0,0 +1,46 @@
+package ch.nuth.zhaw.exbox;
+
+/**
+ * Represents a list with the ability to sort elements.
+ */
+public class MySortedList extends MyList {
+    @Override
+    @SuppressWarnings({ "unchecked", "rawtypes" })
+    public boolean add(Object item) {
+        if (isEmpty()) {
+            return super.add(item);
+        } else {
+            IListNode currentNode = getAnchor().getNextNode();
+
+            while (true) {
+                int comparisonResult;
+
+                try {
+                    if (item instanceof Comparable x &&
+                            currentNode.getItem() instanceof Comparable y) {
+                        comparisonResult = x.compareTo(y);
+                    } else {
+                        throw new UnsupportedOperationException();
+                    }
+                } catch (Exception e) {
+                    comparisonResult = 0;
+                }
+
+                if (comparisonResult == 0) {
+                    insertAfter(currentNode, item);
+                    return true;
+                } else if (comparisonResult < 0) {
+                    insertAfter(currentNode.getPreviousNode(), item);
+                    return true;
+                } else {
+                    currentNode = currentNode.getNextNode();
+
+                    if (currentNode == getAnchor()) {
+                        insertAfter(currentNode.getPreviousNode(), item);
+                        return true;
+                    }
+                }
+            }
+        }
+    }
+}