JavaBean Builder 模式

例如有这个一个类的构造函数：

public Register(int id, int age, String name, String address, String like, int high, int weight)

那么此时的做法：

new Register(1, 20, "A", "B", "C", 170, 60);

这样的缺点就是：

1. 参数会很乱，调用者很容易搞错参数的位置
2. 如果不想为某个参数赋值，那么你还是要赋值，除非你另写一个没有该值的构造函数

Builder模式

public class Register {
    private int id;
    private int age;
    private String name;
    private String address;
    private String like;
    private int high;
    private int weight;

    public static class Builder {
        private int id;
        private String name;
        private int age;
        private String address;
        private String like;
        private int high;
        private int weight;

        public Builder(int id, String name) {
            this.id = id;
            this.name = name;
        }

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

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

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

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

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

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

    //私有化
    private Register(Builder builder){
        id = builder.id;
        name = builder.name;
        age = builder.age;
        address = builder.address;
        like = builder.like;
        high = builder.high;
        weight = builder.weight;
    }
}

此时的用法：

Register re = new Register.Builder(1, "liu").age(20).address("LA").like("Ball").high(180).build();

lombok.Builder 的 @Builder实现