Object-Oriented Design(OOD)

类型

Singleton Pattern

public class Singleton {
  private static Singleton instance = null;
  private Singleton(){
    // Exists only to defeat instantiation.
  }
  public static Singleton getInstance(){
    if(instance==null) instance = new Singleton();
    return instance;
  }
}

Factory Pattern

public class CardGame{
  public static CardGame createCardGame(GameType type){
    if(type == GameType.Poker){
      return new PokerGame();
    }else if(type == GameType.BlackJack){
      return new BlackJackGame();
    }
    return null;
  }
}

Command Pattern

命令模式很好理解，举个例子，司令员下令让士兵去干件事情，从整个事情的角度来考虑，司令员的作用是，发出口令，口令经过传递，传到了士兵耳朵里，士兵去执行。这个过程好在，三者相互解耦，任何一方都不用去依赖其他人，只需要做好自己的事儿就行，司令员要的是结果，不会去关注到底士兵是怎么实现的。

Decorator Pattern

Problem1: Parking Lot

public enum VehicleSize{Motorcycle, Compact, Large}

public abstract class Vehicle{
  private List<ParkingSpot> parkingSpots = new ArrayList<>();
  private String licensePlate;
  private int spotsNeeded;
  private VehicleSize size;
  public int getSpotsNeeded(){return spotsNeeded;}
  public VehicleSize getSize(){return size;}
  public void partInSpot(ParkingSpot s){ parkingSpots.add(s)};
  public void clearSpots(){}
  public abstract boolean canFitInSpot(ParkingSpot spot);
}

public class Bus extends Vehicle {
  public Bus(){
    spotsNeeded = 5;
    size = VehicleSize.Large;
  }
  public boolean canFitInSpot(ParkingSpot spot){}
}
public class Car extends Vehicle {
  public Car(){
    spotsNeeded = 1;
    size = VehicleSize.Compact;
  }
  public boolean canFitInSpot(ParkingSpot spot){}
}
public class Motorcycle extends Vehicle {
  public Motorcycle(){
    spotsNeeded = 1;
    size = VehicleSize.Motorcycle;
  }
  public boolean canFitInSpot(ParkingSpot spot){}
}
public class ParkingLot {
  private Level[] levels;
  private final int NUM_LEVELS = 5;
  public ParkingLot(){}
  public boolean parkVehicle(Vehicle vehicle){}
}
public class Level {
  private int floor;
  private ParkingSpot[] spots;
  private int availableSpots = 0;
  private static final int SPOTS_PER_ROW = 10;
  public Level(int flr, int numberSpots){}
  public int availableSpots(){ return availableSpots;}
  public boolean parkVehicle(Vehicle vehicle){}
  private boolean parkStartingAtSpot(int num, Vehicle v){}
  private int findAvailableSpots(Vehicle vehicle){}
  public void spotFreed(){availableSpots++;}
}
public class ParkingSpot {
  private Vehicle vehicle;
  private VehicleSize spotSize;
  private int row;
  private int spotNumber;
  private Level level;
  public ParkingSpot(Level lvl, int r, int n, VehicleSize s){}
  public boolean isAvailable(){ return vehicle == null};
  public boolean canFitVehicle(Vehicle vehicle){}
  public boolean part(Vehicle v){}
  public int getRow(){ return spotNumber;}
  public void removeVehicle(){}
}

Problem2: Card Game

public class Card{
  public enum Suit{
    CLUBS(1),SPADES(2),HEARTS(3),DIAMONDS(4);
    int value;
    private Suit(int v){ value = v;}
  }
  private int card;
  private Suit suit;
  public Card(int r, Suit s){
    card = r;
    suit = s;
  }
  public int value(){return card;}
  public Suit suit(){return suit;}
}

public class Black extends Card{
    public Black(int r, Suit s){
        super(r,s);
    }
}

Problem3: Elevator

Problem explain1
Problem explain2

Problem4: File System

Problem5: Hotel Reservation

Summary