介紹

我們在一開始介紹單例，假如我們的 App 需要取得會員相關資料，再做事情，例如呼叫 API 什麼的，所以就像以下程式碼

Member member = new Member();
member.setName("AndyAWD");
member.setAge("18");
member.setAddress("Kaohsiung");
member.setPoint("9527");
//對會員資料做事情

但如果某天你沒睡好，把程式碼做了一些修改

Member member = new Member();
member.setName("AndyAWD");
//對會員資料做事情
member.setAge("18");
member.setAddress("Kaohsiung");
member.setPoint("9527");

所以年齡、地址、點數還沒寫入就做事情，這樣就麻煩了，所以我們需要創造者模式（Builder），一次把該寫入的都寫入，中途也不會被插入

Member member = new Member
        .Builder()
        .setName("AndyAWD")
        .setAge("18")
        .setAddress("Kaohsiung")
        .setPoint("9527")
        .build();
//對會員資料做事情

創造者模式實作

1. 在原本的類別內多一個靜態內部類別

public class Member {
    
    public static class Builder {

    }
}    

2. 增加靜態內部類別建構子

public class Member {

    public Member(Builder builder) {

    }        
        
    public static class Builder {

    }
}  

3. 增加設定姓名方法

public class Member {
    
    private String name;

    public Member(Builder builder) {
        this.name = builder.name;
    }        
        
    public static class Builder {
        
        private String name;
        
        public Builder setName(String name) {
            this.name = name;
            return this;
        }
        
    }
}  

4. 增加設定年齡方法

public class Member {
    
    private String name;
    private String age;
    
    public Member(Builder builder) {
        this.name = builder.name;
        this.age = builder.age;
    }        
        
    public static class Builder {
        
        private String name;
        private String age;        
        
        public Builder setName(String name) {
            this.name = name;
            return this;
        }
        
        public Builder setAge(String age) {
            this.age = age;
            return this;
        }        
    }
}  

5. 後面就以此類推