Editing Factory method pattern (section)

====[[Java (programming language)|Java]]====
This [[Java (programming language)|Java]] example is similar to one in the book ''[[Design Patterns]].''

[[File:Maze game UML.svg]]

The <code>MazeGame</code> uses <code>Room</code> but delegates the responsibility of creating <code>Room</code> objects to its subclasses that create the concrete classes. The regular game mode could use this template method:

<syntaxhighlight lang="java">
public abstract class Room {
    abstract void connect(Room room);
}

public class MagicRoom extends Room {
    public void connect(Room room) {}
}

public class OrdinaryRoom extends Room {
    public void connect(Room room) {}
}

public abstract class MazeGame {
     private final List<Room> rooms = new ArrayList<>();

     public MazeGame() {
          Room room1 = makeRoom();
          Room room2 = makeRoom();
          room1.connect(room2);
          rooms.add(room1);
          rooms.add(room2);
     }

     abstract protected Room makeRoom();
}
</syntaxhighlight>

The <code>MazeGame</code> constructor is a [[Template method pattern|template method]] that adds some common logic. It refers to the <code>makeRoom()</code> factory method that encapsulates the creation of rooms such that other rooms can be used in a subclass. To implement the other game mode that has magic rooms, the <code>makeRoom</code> method may be overridden:

<syntaxhighlight lang="java">
public class MagicMazeGame extends MazeGame {
    @Override
    protected MagicRoom makeRoom() {
        return new MagicRoom();
    }
}

public class OrdinaryMazeGame extends MazeGame {
    @Override
    protected OrdinaryRoom makeRoom() {
        return new OrdinaryRoom();
    }
}

MazeGame ordinaryGame = new OrdinaryMazeGame();
MazeGame magicGame = new MagicMazeGame();
</syntaxhighlight>