Builder design pattern in java

Builder設計モード
まとめると、Builder設計モデルは主に次の2つの問題を解決するために使用されます.
1、マルチパラメータオブジェクトの構造2、オブジェクトの構築と表示の分離
「マルチパラメータオブジェクトの構造」を理解するには、次のコードを参照してください.

public class Person
{
   private final String lastName;
   private final String firstName;
   private final String middleName;
   private final String salutation;
   private final String suffix;
   private final String streetAddress;
   private final String city;
   private final String state;
   private final boolean isFemale;
   private final boolean isEmployed;
   private final boolean isHomewOwner;

   public Person(
      final String newLastName,
      final String newFirstName,
      final String newMiddleName,
      final String newSalutation,
      final String newSuffix,
      final String newStreetAddress,
      final String newCity,
      final String newState,
      final boolean newIsFemale,
      final boolean newIsEmployed,
      final boolean newIsHomeOwner)
   {
      this.lastName = newLastName;
      this.firstName = newFirstName;
      this.middleName = newMiddleName;
      this.salutation = newSalutation;
      this.suffix = newSuffix;
      this.streetAddress = newStreetAddress;
      this.city = newCity;
      this.state = newState;
      this.isFemale = newIsFemale;
      this.isEmployed = newIsEmployed;
      this.isHomewOwner = newIsHomeOwner;
   }
}

コードにはパラメータが多すぎて、コードが美しくありません.異なる属性の組合せの構造方法が必要であれば,ここでは多くの構造方法を書く必要があり,これは明らかに科学的ではない.
次に、Builderモードの例を示します.

class Cake {

    private final double sugar;   //cup
    private final double butter;  //cup
    private final int eggs;
    private final int vanila;     //spoon
    private final double flour;   //cup
    private final double bakingpowder; //spoon
    private final double milk;  //cup
    private final int cherry;

    public static class Builder {

        private double sugar;   //cup
        private double butter;  //cup
        private int eggs;
        private int vanila;     //spoon
        private double flour;   //cup
        private double bakingpowder; //spoon
        private double milk;  //cup
        private int cherry;

        //builder methods for setting property
        public Builder sugar(double cup){this.sugar = cup; return this; }
        public Builder butter(double cup){this.butter = cup; return this; }
        public Builder eggs(int number){this.eggs = number; return this; }
        public Builder vanila(int spoon){this.vanila = spoon; return this; }
        public Builder flour(double cup){this.flour = cup; return this; }
        public Builder bakingpowder(double spoon){this.sugar = spoon; return this; }
        public Builder milk(double cup){this.milk = cup; return this; }
        public Builder cherry(int number){this.cherry = number; return this; }


        //return fully build object
        public Cake build() {
            return new Cake(this);
        }
    }

    private Cake(Builder builder) {
        this.sugar = builder.sugar;
        this.butter = builder.butter;
        this.eggs = builder.eggs;
        this.vanila = builder.vanila;
        this.flour = builder.flour;
        this.bakingpowder = builder.bakingpowder;
        this.milk = builder.milk;
        this.cherry = builder.cherry;       
    }

public static void main(String args[]) {
        Cake whiteCake = new Cake.Builder().sugar(1).butter(0.5).  eggs(2).vanila(2).flour(1.5). bakingpowder(0.75).milk(0.5).build();
}

Builderモードはこの問題をよく解決した.
次に、Builderモードが構造と表示の分離を解決するために使用される場合を見てみましょう.

/* "Product" */
class Pizza {
  private String dough = "";
  private String sauce = "";
  private String topping = "";

  public void setDough(String dough)     { this.dough = dough; }
  public void setSauce(String sauce)     { this.sauce = sauce; }
  public void setTopping(String topping) { this.topping = topping; }
}

/* "Abstract Builder" */
abstract class PizzaBuilder {
  protected Pizza pizza;

  public Pizza getPizza() { return pizza; }
  public void createNewPizzaProduct() { pizza = new Pizza(); }

  public abstract void buildDough();
  public abstract void buildSauce();
  public abstract void buildTopping();
}

/* "ConcreteBuilder" */
class HawaiianPizzaBuilder extends PizzaBuilder {
  public void buildDough()   { pizza.setDough("cross"); }
  public void buildSauce()   { pizza.setSauce("mild"); }
  public void buildTopping() { pizza.setTopping("ham+pineapple"); }
}

/* "ConcreteBuilder" */
class SpicyPizzaBuilder extends PizzaBuilder {
  public void buildDough()   { pizza.setDough("pan baked"); }
  public void buildSauce()   { pizza.setSauce("hot"); }
  public void buildTopping() { pizza.setTopping("pepperoni+salami"); }
}

/* "Director" */
class Waiter {
  private PizzaBuilder pizzaBuilder;

  public void setPizzaBuilder(PizzaBuilder pb) { pizzaBuilder = pb; }
  public Pizza getPizza() { return pizzaBuilder.getPizza(); }

  public void constructPizza() {
    pizzaBuilder.createNewPizzaProduct();
    pizzaBuilder.buildDough();
    pizzaBuilder.buildSauce();
    pizzaBuilder.buildTopping();
  }
}

/* A customer ordering a pizza. */
class BuilderExample {
  public static void main(String[] args) {
    Waiter waiter = new Waiter();
    PizzaBuilder hawaiian_pizzabuilder = new HawaiianPizzaBuilder();
    PizzaBuilder spicy_pizzabuilder = new SpicyPizzaBuilder();

    waiter.setPizzaBuilder( hawaiian_pizzabuilder );
    waiter.constructPizza();

    Pizza pizza = waiter.getPizza();
  }
}

Pizzaの作成PizzaBuilderでは、PizzaインタフェースはPizzaの原料のみを定義します.レシピと加工を分離することで、コードがシンプルで美しいだけでなく、拡張メンテナンスも容易になります.