Java中的Builder模式

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1、問題描述

　　Java Builder模式主要是用一個內部類去實例化一個對象，避免一個類出現過多構造函數，而且構造函數如果出現默認參數的話，很容易出錯。

2、具體代碼

package com.mao;

public class User {

    /**賬號*/
    private String userName;

    /**密碼*/
    private String password;

    /**年齡*/
    private int age;

    /**性別*/
    private String sex;

    public String getUserName() {
        return userName;
    }

    public String getPassword() {
        return password;
    }

    public int getAge() {
        return age;
    }

    public String getSex() {
        return sex;
    }

    @Override
    public String toString() {
        return "User{" +
                "userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                ", age=" + age +
                ", sex='" + sex + '\'' +
                '}';
    }

    public static class Builder {

        /**賬號*/
        private String userName;

        /**密碼*/
        private String password;

        /**年齡*/
        private int age;

        /**性別*/
        private String sex;

        public Builder userName(String userName) {
            this.userName = userName;
            return this;
        }

        public Builder password(String password) {
            this.password = password;
            return this;
        }

        public Builder age(int age) {
            this.age = age;
            return this;
        }

        public Builder sex(String sex) {
            this.sex = sex;
            return this;
        }

        public User build() {
            return new User(this);
        }

    }

    private User(Builder b) {
        this.age = b.age;
        this.password = b.password;
        this.sex = b.sex;
        this.userName = b.userName;
    }

    public static void main(String[] args) {
        User user = new Builder().age(10).password("abc").sex("男").userName("張三").build();
        System.out.println(user.toString());
    }

}

3、參考網站

　　https://www.cnblogs.com/begin1949/p/4930896.html