Builder pattern

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Builder pattern application scenarios ：

It is mainly used to build some complex objects , Here's a complex object like ： When building buildings , We need to lay the foundation first , Building framework , And then cover it from bottom to top . Usually , In the construction of such complex structures , It's hard to do it all at once . We need to build parts of this object first , And then put them together in stages . So now there's the builder pattern ： The builder pattern is made up of Builder（ builder ） and Director（ commander ） form . Please see the following UML chart ：                    

                                    

 

Director class package com.yuan.builder.demo1; // command : The core , Responsible for directing the construction of a project , How the project builds , It's up to it public class Director { // Instruct the workers to give the order of execution public Product build(Builder builder) { builder.buildA(); builder.buildC(); builder.buildD(); builder.buildB(); return builder.getProduct(); } }   Builder class   package com.yuan.builder.demo1; // The abstract builder public abstract class Builder { abstract void buildA();// The foundation abstract void buildB();// Steel Engineering abstract void buildC();// Laying wires abstract void buildD();// Paint // to be finished ： Got a specific product abstract Product getProduct(); } Worker class package com.yuan.builder.demo1; /** * The concrete builder : Worker */ public class Worker extends Builder { private Product product; public Worker() { this.product = new Product(); } @Override void buildA() { product.setBuildA(" The foundation "); System.out.println(" The foundation "); } @Override void buildB() { product.setBuildB(" Steel Engineering "); System.out.println(" Steel Engineering "); } @Override void buildC() { pro.........