- 起源：cipher
- ciphermagic.cn/java8-builder.html
程序员常常会遇到灵魂拷问：你有对象吗？
没有，但我能够 new 一个！
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<String> hobby;private String birthday;private String address;private String mobile;private String email;private String hairColor;private Map<String, String> gift;// 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); myGirlFriend.setHips(33); myGirlFriend.setBirthday("2001-10-26"); myGirlFriend.setAddress("上海浦东"); myGirlFriend.setMobile("18688888888"); myGirlFriend.setEmail("pretty-xiaomei@qq.com"); myGirlFriend.setHairColor("浅棕色带点微卷"); List<String> hobby = new ArrayList<>(); hobby.add("逛街"); hobby.add("购物"); hobby.add("买货色"); myGirlFriend.setHobby(hobby); Map<String, String> gift = new HashMap<>(); gift.put("情人节礼物", "LBR 1912女王时代"); gift.put("生日礼物", "迪奥烈焰蓝金"); gift.put("纪念日礼物", "阿玛尼红管唇釉"); myGirlFriend.setGift(gift);// 等等等等 ... }}--
GirlFriend{name='小美', age=18, bust=33, waist=23, hips=33, hobby=[逛街, 购物, 买货色], birthday='2001-10-26', address='上海浦东', mobile='18688888888', email='pretty-xiaomei@qq.com', hairColor='浅棕色带点微卷', gift={情人节礼物=LBR 1912女王时代, 生日礼物=迪奥烈焰蓝金, 纪念日礼物=阿玛尼红管唇釉}}GirlFriend 是很美，但写起来也太麻烦了吧。
说说毛病：实例化和设置属性离开，不好保护；变量名反复写。
莫慌，看法宝~
这里不再介绍其余 Builder 实现形式，间接祭出最实用的通用 Builder：
实用于所有类，不须要革新原来类，不须要 lombok 插件反对。
先看看应用姿态：
public class GirlFriend {// 省略属性 ...// 省略 getter & setter ...// 为了演示不便，加几个聚合办法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, "买货色") .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，清新！
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<T> { private final Supplier<T> instantiator; private List<Consumer<T>> modifiers = new ArrayList<>(); public Builder(Supplier<T> instantiator) { this.instantiator = instantiator; } public static <T> Builder<T> of(Supplier<T> instantiator) { return new Builder<>(instantiator); } public <P1> Builder<T> with(Consumer1<T, P1> consumer, P1 p1) { Consumer<T> c = instance -> consumer.accept(instance, p1); modifiers.add(c); return this; } public <P1, P2> Builder<T> with(Consumer2<T, P1, P2> consumer, P1 p1, P2 p2) { Consumer<T> c = instance -> consumer.accept(instance, p1, p2); modifiers.add(c); return this; } public <P1, P2, P3> Builder<T> with(Consumer3<T, P1, P2, P3> consumer, P1 p1, P2 p2, P3 p3) { Consumer<T> 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); }}这个示例最多反对三个参数的设置属性办法，也齐全够用了。如果要扩大也很容易，依葫芦画瓢，增加多个参数的Consumer。
快用你的 Builder 建个对象吧~
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