• Builder一个对象


    一般新建对象我们都是直接new一下

    public class GirlFriend {
    private String name;
    private int age;
    // 省略 getter & setter ...
    public static void main(String[] args) {
    GirlFriend myGirlFriend = new GirlFriend();
    myGirlFriend.setName("小美");
    myGirlFriend.setAge(18);
    }
    }
    没问题,老铁!但如果对象的属性太多,咋办?

    public class GirlFriend {
    private String name;
    private int age;
    private int bust;
    private int waist;
    private int hips;
    private List hobby;
    // 等等等等 ...
    // 省略 getter & setter ...
    public static void main(String[] args) {
    GirlFriend myGirlFriend = new GirlFriend();
    myGirlFriend.setName("小美");
    myGirlFriend.setAge(18);
    myGirlFriend.setBust(33);
    myGirlFriend.setWaist(23);
    // 等等等等 ...
    }
    }

    而Java8通用Builder适用于所有类,不需要改造原来类,不需要 lombok 插件支持。

    先看看使用姿势:

    public class GirlFriend {
    // 省略属性 ...
    // 省略 getter & setter ...

    // 为了演示方便,加几个聚合方法
    public void addHobby(String hobby) {
        this.hobby = Optional.ofNullable(this.hobby).orElse(new ArrayList<>());
        this.hobby.add(hobby);
    }
    public void addGift(String day, String gift) {
        this.gift = Optional.ofNullable(this.gift).orElse(new HashMap<>());
        this.gift.put(day, gift);
    }
    public void setVitalStatistics(int bust, int waist, int hips) {
        this.bust = bust;
        this.waist = waist;
        this.hips = hips;
    }
    public static void main(String[] args) {
        GirlFriend myGirlFriend = Builder.of(GirlFriend::new)
                .with(GirlFriend::setName, "小美")
                .with(GirlFriend::setAge, 18)
                .with(GirlFriend::setVitalStatistics, 33, 23, 33)
                .with(GirlFriend::setBirthday, "2001-10-26")
                .with(GirlFriend::setAddress, "上海浦东")
                .with(GirlFriend::setMobile, "18688888888")
                .with(GirlFriend::setEmail, "pretty-xiaomei@qq.com")
                .with(GirlFriend::setHairColor, "浅棕色带点微卷")
                .with(GirlFriend::addHobby, "逛街")
                .with(GirlFriend::addHobby, "购物")
                .with(GirlFriend::addHobby, "买东西")
                .with(GirlFriend::addGift, "情人节礼物", "LBR 1912女王时代")
                .with(GirlFriend::addGift, "生日礼物", "迪奥烈焰蓝金")
                .with(GirlFriend::addGift, "纪念日礼物", "阿玛尼红管唇釉")
                // 等等等等 ...
                .build();
    }
    

    }
    看到了吗!实例化和属性设置在同一条语句执行,链式操作,一路点点点,清爽!

    Talk is cheap, show me the code:

    /**

    • 通用的 Builder 模式构建器
    • @author: CipherCui
    • @since 2019/8/29
      /
      public class Builder {
      private final Supplier instantiator;
      private List<Consumer> modifiers = new ArrayList<>();
      public Builder(Supplier instantiator) {
      this.instantiator = instantiator;
      }
      public static Builder of(Supplier instantiator) {
      return new Builder<>(instantiator);
      }
      public Builder with(Consumer1<T, P1> consumer, P1 p1) {
      Consumer c = instance -> consumer.accept(instance, p1);
      modifiers.add(c);
      return this;
      }
      public <P1, P2> Builder with(Consumer2<T, P1, P2> consumer, P1 p1, P2 p2) {
      Consumer c = instance -> consumer.accept(instance, p1, p2);
      modifiers.add(c);
      return this;
      }
      public <P1, P2, P3> Builder with(Consumer3<T, P1, P2, P3> consumer, P1 p1, P2 p2, P3 p3) {
      Consumer c = instance -> consumer.accept(instance, p1, p2, p3);
      modifiers.add(c);
      return this;
      }
      public T build() {
      T value = instantiator.get();
      modifiers.forEach(modifier -> modifier.accept(value));
      modifiers.clear();
      return value;
      }
      /
      *
      • 1 参数 Consumer
        /
        @FunctionalInterface
        public interface Consumer1<T, P1> {
        void accept(T t, P1 p1);
        }
        /
        *
      • 2 参数 Consumer
        /
        @FunctionalInterface
        public interface Consumer2<T, P1, P2> {
        void accept(T t, P1 p1, P2 p2);
        }
        /
        *
      • 3 参数 Consumer
        */
        @FunctionalInterface
        public interface Consumer3<T, P1, P2, P3> {
        void accept(T t, P1 p1, P2 p2, P3 p3);
        }
        }
        这个示例最多支持三个参数的设置属性方法,也完全够用了。如果要扩展也很容易,依葫芦画瓢,添加多个参数的Consumer。

    参考:http://www.ciphermagic.cn/java8-builder.html

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  • 原文地址:https://www.cnblogs.com/chen-chen-chen/p/12201556.html
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