【设计模式】JAVA Design Patterns——Abstract Factory（抽象工厂模式）

public interface Castle {
  String getDescription();
}
 
public interface King {
  String getDescription();
}
 
public interface Army {
  String getDescription();
}
 
// Elven implementations ->
public class ElfCastle implements Castle {
  static final String DESCRIPTION = "This is the Elven castle!";
  @Override
  public String getDescription() {
    return DESCRIPTION;
  }
}
public class ElfKing implements King {
  static final String DESCRIPTION = "This is the Elven king!";
  @Override
  public String getDescription() {
    return DESCRIPTION;
  }
}
public class ElfArmy implements Army {
  static final String DESCRIPTION = "This is the Elven Army!";
  @Override
  public String getDescription() {
    return DESCRIPTION;
  }
}
 
// Orcish implementations similarly -> ...
 

public interface KingdomFactory {
  Castle createCastle();
  King createKing();
  Army createArmy();
}
 
public class ElfKingdomFactory implements KingdomFactory {
  public Castle createCastle() {
    return new ElfCastle();
  }
  public King createKing() {
    return new ElfKing();
  }
  public Army createArmy() {
    return new ElfArmy();
  }
}
 
public class OrcKingdomFactory implements KingdomFactory {
  public Castle createCastle() {
    return new OrcCastle();
  }
  public King createKing() {
    return new OrcKing();
  }
  public Army createArmy() {
    return new OrcArmy();
  }
}

var factory = new ElfKingdomFactory();
var castle = factory.createCastle();
var king = factory.createKing();
var army = factory.createArmy();
 
castle.getDescription();
king.getDescription();
army.getDescription();

This is the Elven castle!
This is the Elven king!
This is the Elven Army!

public static class FactoryMaker {
 
    public enum KingdomType {
        ELF, ORC
    }
 
    public static KingdomFactory makeFactory(KingdomType type) {
        return switch (type) {
            case ELF -> new ElfKingdomFactory();
            case ORC -> new OrcKingdomFactory();
            default -> throw new IllegalArgumentException("KingdomType not supported.");
        };
    }
}
 
    public static void main(String[] args) {
        var app = new App();
 
        LOGGER.info("Elf Kingdom");
        app.createKingdom(FactoryMaker.makeFactory(KingdomType.ELF));
        LOGGER.info(app.getArmy().getDescription());
        LOGGER.info(app.getCastle().getDescription());
        LOGGER.info(app.getKing().getDescription());
 
        LOGGER.info("Orc Kingdom");
        app.createKingdom(FactoryMaker.makeFactory(KingdomType.ORC));
        --similar use of the orc factory
    }