当对象成员变量太多时，使用建造方法给变量赋值往往变得很臃肿，所以可以这样做

public class Something {private String a;private String b;private String c;private String d;private String e;public Something(Builder builder) {this.a = builder.a;this.b = builder.b;this.c = builder.c;this.d = builder.d;this.e = builder.e;}static class Builder{private String a;private String b;private String c;private String d;private String e;public Builder setA(String a) {this.a = a;return this;}public Builder setB(String b) {this.b = b;return this;}public Builder setC(String c) {this.c = c;return this;}public Builder setD(String d) {this.d = d;return this;}public Builder setE(String e) {this.e = e;return this;}public Something build() {return new Something(this);}}public static void main(String[] args) {Something something = new Something.Builder().setA("a").setB("b").setC("c").setD("d").setE("e").build();System.out.println(something.a);}

对传统建造者模式的理解

传统建造者模式，可以将实体类中的部分属性抽象出来并单独建造，并且实体的构建过程交予构造者。我认为这是外观模式和策略模式的结合。

关于传统建造者模式可以看如下文章

秒懂设计模式之建造者模式（Builder pattern） - shusheng007的文章 - 知乎