effective java之使用构建器来创建对象

第二章第2条:遇到多个构造器参数时要考虑使用构建器(builder)

就是建造者模式(不直接生成想要的对象，而是让客户端利用所有有必要的参数调用构造器或者静态工厂)直接上代码

package com.edu.character02;

/**
 * <p>
 * builder Pattern
 * </p>
 *
 * @作者 five-five
 * @创建时间 2020/8/4
 */
public class Student {
    private int id;//必填
    private String name;//必填
    private String sex;
    private String address;

    public static class Builder {
        private final int id;//必填
        private final String name;//必填
        private String sex = "男";
        private String address = "湖南";

        //返回对象，可以流式编写代码
        public Builder(int id, String name) {
            this.id = id;
            this.name = name;
        }

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

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

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

    private Student(Builder builder) {
        this.id = builder.id;
        this.name = builder.name;
        this.sex = builder.sex;
        this.address = builder.address;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

测试代码：

package com.edu.character02;

/**
 * @作者 five-five
 * @创建时间 2020/8/4
 */
public class TestStudent {
    public static void main(String[] args) {
        Student student=new Student.Builder(1,"鸣人").sex("男").address("湖南").build();
        System.out.println(student);
    }
}

测试结果：