你還在 new 對(duì)象嗎？Java8 通用 Builder 了解一下
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作者：cipher
www.ciphermagic.cn/java8-builder.html
沒(méi)有，但我可以 new 一個(gè)！
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);
}
}
沒(méi)問(wèn)題，老鐵！但如果對(duì)象的屬性太多，咋辦？
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("上海浦東");
myGirlFriend.setMobile("18688888888");
myGirlFriend.setEmail("[email protected]");
myGirlFriend.setHairColor("淺棕色帶點(diǎn)微卷");
List<String> hobby = new ArrayList<>();
hobby.add("逛街");
hobby.add("購(gòu)物");
hobby.add("買(mǎi)東西");
myGirlFriend.setHobby(hobby);
Map<String, String> gift = new HashMap<>();
gift.put("情人節(jié)禮物", "LBR 1912女王時(shí)代");
gift.put("生日禮物", "迪奧烈焰藍(lán)金");
gift.put("紀(jì)念日禮物", "阿瑪尼紅管唇釉");
myGirlFriend.setGift(gift);
// 等等等等 ...
}
}
GirlFriend{name='小美'
, age=18
, bust=33
, waist=23
, hips=33
, hobby=[逛街, 購(gòu)物, 買(mǎi)東西]
, birthday='2001-10-26'
, address='上海浦東'
, mobile='18688888888'
, email='[email protected]'
, hairColor='淺棕色帶點(diǎn)微卷'
, gift={情人節(jié)禮物=LBR 1912女王時(shí)代, 生日禮物=迪奧烈焰藍(lán)金, 紀(jì)念日禮物=阿瑪尼紅管唇釉}
}
莫慌，看法寶~
public class GirlFriend {
// 省略屬性 ...
// 省略 getter & setter ...
// 為了演示方便，加幾個(gè)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, "上海浦東")
.with(GirlFriend::setMobile, "18688888888")
.with(GirlFriend::setEmail, "[email protected]")
.with(GirlFriend::setHairColor, "淺棕色帶點(diǎn)微卷")
.with(GirlFriend::addHobby, "逛街")
.with(GirlFriend::addHobby, "購(gòu)物")
.with(GirlFriend::addHobby, "買(mǎi)東西")
.with(GirlFriend::addGift, "情人節(jié)禮物", "LBR 1912女王時(shí)代")
.with(GirlFriend::addGift, "生日禮物", "迪奧烈焰藍(lán)金")
.with(GirlFriend::addGift, "紀(jì)念日禮物", "阿瑪尼紅管唇釉")
// 等等等等 ...
.build();
}
}
Talk is cheap, show me the code：
/**
* 通用的 Builder 模式構(gòu)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 參數(shù) Consumer
*/
@FunctionalInterface
public interface Consumer1<T, P1> {
void accept(T t, P1 p1);
}
/**
* 2 參數(shù) Consumer
*/
@FunctionalInterface
public interface Consumer2<T, P1, P2> {
void accept(T t, P1 p1, P2 p2);
}
/**
* 3 參數(shù) Consumer
*/
@FunctionalInterface
public interface Consumer3<T, P1, P2, P3> {
void accept(T t, P1 p1, P2 p2, P3 p3);
}
}
快用你的 Builder 建個(gè)對(duì)象吧~
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