diff --git a/src/main/java/_7/_3/PersonTest.java b/src/main/java/_7/_3/PersonTest.java
new file mode 100644
index 0000000..21aa148
--- /dev/null
+++ b/src/main/java/_7/_3/PersonTest.java
@@ -0,0 +1,117 @@
+package _7._3;
+
+import java.io.*;
+import java.util.ArrayList;
+import java.util.List;
+
+class Person implements Serializable {
+	private String firstname;
+	private String lastname;
+	private transient String sortname;
+
+	public Person() { }
+	public Person(String firstname, String lastname) {
+		this.firstname = firstname;
+		this.lastname = lastname;
+		updateSortname();
+	}
+	public String getFirstname() {
+		return firstname;
+	}
+	public void setFirstname(String firstname) {
+		this.firstname = firstname;
+		updateSortname();
+	}
+	public String getLastname() {
+		return lastname;
+	}
+	public void setLastname(String lastname) {
+		this.lastname = lastname;
+		updateSortname();
+	}
+	public String getSortname() {
+		return sortname;
+	}
+	public void updateSortname() {
+		sortname = lastname + firstname;
+	}
+
+	@Override
+	public String toString() {
+		return firstname + " " + lastname + " (" + sortname + ")";
+	}
+
+
+	public static List<Person> load(String filename) throws IOException {
+		List<Person> people = new ArrayList<>();
+		try (DataInputStream in = new DataInputStream(new BufferedInputStream(
+				new FileInputStream(filename)))) {
+			boolean nextExists = in.readBoolean();
+			while (nextExists) {
+				people.add(load(in));
+				nextExists = in.readBoolean();
+			}
+		}
+		return people;
+	}
+
+	public static Person load(DataInputStream in) throws IOException {
+		return new Person(in.readUTF(),in.readUTF());
+	}
+
+
+	public static void save(String filename, List<Person> list) throws IOException {
+		try (DataOutputStream out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(filename)))) {
+			for (Person p : list) {
+				out.writeBoolean(true);
+				save(out, p);
+			}
+			out.writeBoolean(false);
+		}
+	}
+
+	public static void save(DataOutputStream out, Person person) throws IOException {
+		out.writeUTF(person.getFirstname());
+		out.writeUTF(person.getLastname());
+	}
+
+
+	@SuppressWarnings("unchecked")
+	public static List<Person> unserialize(String filename) throws IOException, ClassNotFoundException {
+		List<Person> people;
+		try (ObjectInputStream in = new ObjectInputStream(
+				new BufferedInputStream(new FileInputStream(filename)))) {
+			people = (List<Person>) in.readObject();
+			for (Person p : people) {
+				p.updateSortname();
+			}
+		}
+		return people;
+	}
+
+	public static void serialize(String filename, List<Person> persons) throws IOException {
+		try (ObjectOutputStream out = new ObjectOutputStream(
+				new BufferedOutputStream(new FileOutputStream(filename)))) {
+			out.writeObject(persons);
+		}
+	}
+}
+
+public class PersonTest {
+
+	public static void main(String[] args) throws IOException, ClassNotFoundException {
+		List<Person> persons = new ArrayList<>();
+		persons.add(new Person("Willy", "Wonka"));
+		persons.add(new Person("Charlie", "Bucket"));
+		persons.add(new Person("Grandpa", "Joe"));
+		System.out.println(persons);
+		
+		Person.save("persons.sav", persons);
+		persons = Person.load("persons.sav");
+		System.out.println(persons);
+		Person.serialize("persons.ser", persons);
+		persons = Person.unserialize("persons.ser");
+		System.out.println(persons);
+	}
+
+}