diff --git a/Exercise.java b/Exercise.java
index df7ea05..681154c 100644
--- a/Exercise.java
+++ b/Exercise.java
@@ -1,17 +1,19 @@
+import java.util.HashMap;
+
 public class Exercise {
 
   public static void main(String[] args) {
-    TelephoneBook telephoneBook = new TelephoneBook();
+    TelephoneBook telephoneBook = new TelephoneBook(new HashMap<>());
 
     telephoneBook.addEntry(
-        new TelephoneBook.Person("Hans Maier"),
-        new TelephoneBook.TelephoneNumber("+49 67234 887261"));
+        new Person("Hans Maier"),
+        new TelephoneNumber("+49 67234 887261"));
     telephoneBook.addEntry(
-        new TelephoneBook.Person("Peter Mueller"),
-        new TelephoneBook.TelephoneNumber("+49 7529 87612"));
+        new Person("Peter Mueller"),
+        new TelephoneNumber("+49 7529 87612"));
     telephoneBook.addEntry(
-        new TelephoneBook.Person("Lisa Schmidt"),
-        new TelephoneBook.TelephoneNumber("+49 8762 52081"));
+        new Person("Lisa Schmidt"),
+        new TelephoneNumber("+49 8762 52081"));
 
     System.out.println(telephoneBook.getTelephoneNumberByName("Hans Maier"));
   }
diff --git a/Person.java b/Person.java
new file mode 100644
index 0000000..c48d48c
--- /dev/null
+++ b/Person.java
@@ -0,0 +1,2 @@
+public record Person(String name) {
+}
diff --git a/TelephoneBook.java b/TelephoneBook.java
index 077090e..0303a68 100644
--- a/TelephoneBook.java
+++ b/TelephoneBook.java
@@ -1,24 +1,17 @@
 import java.util.HashMap;
-import java.util.Map.Entry;
+import java.util.Map;
 
-public class TelephoneBook {
+public record TelephoneBook(HashMap<Person, TelephoneNumber> entries) {
+	public void addEntry(Person person, TelephoneNumber telephoneNumber) {
+		entries.put(person, telephoneNumber);
+	}
 
-  private HashMap<Person, TelephoneNumber> entries = new HashMap<>();
-
-  public void addEntry(Person person, TelephoneNumber telephoneNumber) {
-    entries.put(person, telephoneNumber);
-  }
-
-  public TelephoneNumber getTelephoneNumberByName(String name) {
-    for (Entry<Person, TelephoneNumber> entry : entries.entrySet()) {
-      if (entry.getKey().name().equals(name)) {
-        return entry.getValue();
-      }
-    }
-    return null;
-  }
-
-  public record Person(String name) {}
-
-  public record TelephoneNumber(String value) {}
+	public TelephoneNumber getTelephoneNumberByName(String name) {
+		for (Map.Entry<Person, TelephoneNumber> entry : entries.entrySet()) {
+			if (entry.getKey().name().equals(name)) {
+				return entry.getValue();
+			}
+		}
+		return null;
+	}
 }
diff --git a/TelephoneNumber.java b/TelephoneNumber.java
new file mode 100644
index 0000000..529d7e7
--- /dev/null
+++ b/TelephoneNumber.java
@@ -0,0 +1,2 @@
+public record TelephoneNumber(String number) {
+}