Builder建造者/建構者模式-設計模式-建立型

針對建構一個對象時，該對象有多個屬性，建構比較複雜，容易出錯 ，且如果直接用構造方法建構的話，為了保證多種需求，有的參數不需要傳，有的需要傳，一共有10個屬性，你需要無參構造、一個參數的構造方法、兩個參數的構造方法...一堆構造方法。

為了解決這個問題，可以使用建造者模式。

package creational.builder;

public class Person {
    int id;
    String name;
    int age;
    double weight;
    int score;
    Location loc;

    private Person() {}

    @Override
    public String toString() {
        return "Person{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", weight=" + weight +
                ", score=" + score +
                ", loc=" + loc +
                '}';
    }

    public static class PersonBuilder {
        Person p = new Person();

        public PersonBuilder basicInfo(int id, String name, int age) {
            p.id = id;
            p.name = name;
            p.age = age;
            return this;
        }

        public PersonBuilder weight(double weight) {
            p.weight = weight;
            return this;
        }

        public PersonBuilder score(int score) {
            p.score = score;
            return this;
        }

        public PersonBuilder loc(String street, String roomNo) {
            p.loc = new Location(street, roomNo);
            return this;
        }

        public Person build() {
            return p;
        }
    }



}

           

package creational.builder;

public class Main {
    public static void main(String[] args) {
        Person p = new Person.PersonBuilder()
                .basicInfo(1, "zhangsan", 18)
                //.score(20)
                .weight(200)
                //.loc("bj", "23")
                .build();
        System.out.println(p.toString());
    }
}
           

以上代碼可以看到，先基于Bulider對象進行初始化指派完善，完成後，調用build()方法，得到最終的要建構的對象。

https://github.com/phs999/DesignPatterns/tree/c6cc68d93db4c096b8362ad2e48f188760c3c167/design_pattern/src/creational/builder