JAVAEE细细看 设计模式1 - 建造者模式

建造者模式

开闭原则： 对修改关闭，对扩展开放

最终结果

		// 加几个参数，随意
        Product product = new Builder(1).color("red").market("12").size("13").type("格子衬衫").build();
        或者
        Product product = new Builder(1).size("13").type("格子衬衫").build();
        或者一个都不加
        Product product = new Builder(1).build();

--- 很巧妙的，不用再为构造方法发愁，pojo中添加了新的字段，也不用重新生成或者修改构造方法，

直接上示例

package com.ittest;

public class Product {
    private Integer id;
    private String color;
    private String size;
    private  String type;

    // 新增
    private String market;

    // 核心，赋值
    public Product(Builder builder) {
        this.id = builder.id;
        this.type = builder.type;
        this.size = builder.size;
        this.color = builder.color;
        this.market = builder.market;
    }

    public static class Builder {
       private Integer id;
       private String color;
       private String size;
       private  String type;

       // 新增 一个
       private String market;

       public Builder(Integer id) {
           this.id = id;
       }

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

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

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

       // 新增
       public Builder market(String market){
           this.market = market;
           return this;
       }

       // 核心，最后调用build才会赋值
       public Product build(){
           return new Product(this);
       }
   }

   // 测试
    public static void main(String[] args) {

        // 加几个参数，随意
        Product product = new Builder(1).color("red").market("12").size("13").type("格子衬衫").build();

        System.out.println(product);// 可以重写tostring方法，打印看看
    }
}