◆建造者模式也属于创建型模式，它提供了一种创建对象的最佳方式。
◆定义: 将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的表示
◆主要作用:在用户不知道对象的建造过程和细节的情况下就可以直接创建复杂的对象。
◆用户只需要给出指定复杂对象的类型和内容，建造者模式负责按顺序创建复杂对象(把内部的建造过程和细
节隐藏起来)
◆例子:
例一：
//指挥：核心，负责指挥建造一个工程，工程如何建造有它决定
public class Director {
//指挥工人按顺序建房子
public Product build(Builder builder){
builder.buildA();
builder.buildB();
builder.buildC();
builder.buildD();
return builder.getProduct();
}
}
//抽象的建造者:方法
public abstract class Builder {
abstract void buildA();//地基
abstract void buildB();//钢筋工程
abstract void buildC();//铺电线
abstract void buildD();//粉刷
//完工：得到产品
abstract Product getProduct();
}
//具体建造者：工人
public class Worker extends Builder{
private Product product;
public Worker(){
product = new Product();
}
@Override
void buildA() {
product.setBuildA("建地基");
System.out.println("建地基");
}
@Override
void buildB() {
product.setBuildB("钢筋工程");
System.out.println("钢筋工程");
}
@Override
void buildC() {
product.setBuildC("铺电线");
System.out.println("铺电线");
}
@Override
void buildD() {
product.setBuildD("粉刷");
System.out.println("粉刷");
}
@Override
Product getProduct() {
return product;
}
}
//产品：房子
public class Product {
private String buildA;
private String buildB;
private String buildC;
private String buildD;
public String getBuildA() { return buildA; }
public void setBuildA(String buildA) { this.buildA = buildA; }
public String getBuildB() { return buildB; }
public void setBuildB(String buildB) { this.buildB = buildB; }
public String getBuildC() { return buildC; }
public void setBuildC(String buildC) { this.buildC = buildC; }
public String getBuildD() { return buildD; }
public void setBuildD(String buildD) { this.buildD = buildD; }
}
public class Test {
public static void main(String[] args) {
//指挥
Director director = new Director();
//z指挥具体的工人完成产品
Product build = director.build(new Worker());
System.out.println(build.toString());
}
}
例二
代码如下：
public class
BuilderPatternDemo1 {
public static void main(String[] args) {
//盖普通房子
CommonHouse commonHouse = new CommonHouse();
//准备创建房子的指挥者
HouseDirector houseDirector = new HouseDirector(commonHouse);
//完成盖房子，返回产品(普通房子)
House house = houseDirector.constructHouse();
//System.out.println("输出流程");
System.out.println("--------------------------");
//盖高楼
HighBuilding highBuilding = new HighBuilding();
//重置建造者
houseDirector.setHouseBuilder(highBuilding);
//完成盖房子，返回产品(高楼)
houseDirector.constructHouse();
}
}
/**
* 产品
*/
class House {
private String baise;
private String wall;
private String roofed;
public String getBaise() {
return baise;
}
public void setBaise(String baise) {
this.baise = baise;
}
public String getWall() {
return wall;
}
public void setWall(String wall) {
this.wall = wall;
}
public String getRoofed() {
return roofed;
}
public void setRoofed(String roofed) {
this.roofed = roofed;
}
}
// 抽象的建造者
abstract class HouseBuilder {
protected House house = new House();
//将建造的流程写好, 抽象的方法
public abstract void buildBasic();
public abstract void buildWalls();
public abstract void roofed();
//建造房子好， 将产品(房子) 返回
public House buildHouse() {
return house;
}
}
class CommonHouse extends HouseBuilder {
@Override
public void buildBasic() {
// TODO Auto-generated method stub
System.out.println(" 普通房子打地基5米 ");
}
@Override
public void buildWalls() {
// TODO Auto-generated method stub
System.out.println(" 普通房子砌墙10cm ");
}
@Override
public void roofed() {
// TODO Auto-generated method stub
System.out.println(" 普通房子屋顶 ");
}
}
class HighBuilding extends HouseBuilder {
@Override
public void buildBasic() {
// TODO Auto-generated method stub
System.out.println(" 高楼的打地基100米 ");
}
@Override
public void buildWalls() {
// TODO Auto-generated method stub
System.out.println(" 高楼的砌墙20cm ");
}
@Override
public void roofed() {
// TODO Auto-generated method stub
System.out.println(" 高楼的透明屋顶 ");
}
}
//指挥者，这里去指定制作流程，返回产品
class HouseDirector {
HouseBuilder houseBuilder = null;
//构造器传入 houseBuilder
public HouseDirector(HouseBuilder houseBuilder) {
this.houseBuilder = houseBuilder;
}
//通过setter 传入 houseBuilder
public void setHouseBuilder(HouseBuilder houseBuilder) {
this.houseBuilder = houseBuilder;
}
//如何处理建造房子的流程，交给指挥者
public House constructHouse() {
houseBuilder.buildBasic();
houseBuilder.buildWalls();
houseBuilder.roofed();
return houseBuilder.buildHouse();
}
}
上面示例是Builder模式的常规用法，导演类Director在Builder模式中具有很重要的作用，它用于指导具体构建者如何构建产品，控制调用先后次序，并向调用者返回完整的产品类，但是有些情况下需要简化系统结构，可以把Director和抽象建造者进行结合。
通过静态内部类方式实现零件无序装配构造，这种方式使用更加灵活，更符合定义。内部有复杂对象的默认实现，使用时可以根据用户需求自由定义更改内容,并且无需改变具体的构造方式。就可以生产出不同复杂产品
比如:比如麦当劳的套餐,服务员(具体建造者)可以随意搭配任意几种产品(零件)组成一款套餐(产品)，然后出售给客户。比第一种方式少 了指挥者，主要是因为第二种方式把指挥者交给用户来操作，使得产品的创建更加简单灵活。
例三： 没有指挥者参与
//建造者
public abstract class Builder {
abstract Builder buildA(String msg); //汉堡
abstract Builder buildB(String msg); //可乐
abstract Builder buildC(String msg); //薯条
abstract Builder buildD(String msg); //甜点
abstract Product getProduct();
}
public class Worker extends Builder{
private Product product;
public Worker(){ product = new Product(); }
@Override
Builder buildA(String msg) {
product.setBuildA(msg);
return this;
}
@Override
Builder buildB(String msg) {
product.setBuildB(msg);
return this;
}
@Override
Builder buildC(String msg) {
product.setBuildC(msg);
return this;
}
@Override
Builder buildD(String msg) {
product.setBuildD(msg);
return this;
}
@Override
Product getProduct() {
return product;
}
}
//产品：套餐
public class Product {
private String BuildA = "汉堡";
private String BuildB = "可乐";
private String BuildC = "薯条";
private String BuildD = "甜点";
public String getBuildA() { return BuildA; }
public void setBuildA(String buildA) { BuildA = buildA; }
public String getBuildB() { return BuildB; }
public void setBuildB(String buildB) { BuildB = buildB; }
public String getBuildC() { return BuildC; }
public void setBuildC(String buildC) { BuildC = buildC; }
public String getBuildD() { return BuildD; }
public void setBuildD(String buildD) { BuildD = buildD; }
@Override
public String toString() {
return "Product{" +
"BuildA='" + BuildA + '\'' +
", BuildB='" + BuildB + '\'' +
", BuildC='" + BuildC + '\'' +
", BuildD='" + BuildD + '\'' +
'}';
}
}
public class Test {
public static void main(String[] args) {
//服务员
Worker worker = new Worker();
//Product product = worker.getProduct();
// System.out.println(product.toString());
//链式编程 :在原来基础上可以自由组合
Product product = worker.buildA("鸡肉卷").buildB("橘子汽水").getProduct();
System.out.println(product.toString());
}
}
例四：
import java.util.ArrayList;
import java.util.List;
/**
* @anthor longzx
* @create 2021 03 15 22:45
* @Description
**/
public class BuilderPatternDemo2 {
public static void main(String[] args) {
MealBuilder mealBuilder = new MealBuilder();
Meal vegMeal = mealBuilder.prepareVegMeal();
System.out.println("Veg Meal");
vegMeal.showItems();
System.out.println("Total Cost: " +vegMeal.getCost());
Meal nonVegMeal = mealBuilder.prepareNonVegMeal();
System.out.println("\n\nNon-Veg Meal");
nonVegMeal.showItems();
System.out.println("Total Cost: " +nonVegMeal.getCost());
}
}
interface Item {
public String name();
public Packing packing();
public float price();
}
interface Packing {
public String pack();
}
class Wrapper implements Packing {
@Override
public String pack() {
return "Wrapper";
}
}
class Bottle implements Packing {
@Override
public String pack() {
return "Bottle";
}
}
abstract class Burger implements Item {
@Override
public Packing packing() {
return new Wrapper();
}
@Override
public abstract float price();
}
abstract class ColdDrink implements Item {
@Override
public Packing packing() {
return new Bottle();
}
@Override
public abstract float price();
}
class VegBurger extends Burger {
@Override
public float price() {
return 25.0f;
}
@Override
public String name() {
return "Veg Burger";
}
}
class ChickenBurger extends Burger {
@Override
public float price() {
return 50.5f;
}
@Override
public String name() {
return "Chicken Burger";
}
}
class Coke extends ColdDrink {
@Override
public float price() {
return 30.0f;
}
@Override
public String name() {
return "Coke";
}
}
class Pepsi extends ColdDrink {
@Override
public float price() {
return 35.0f;
}
@Override
public String name() {
return "Pepsi";
}
}
/**
* 产品
*/
class Meal {
private List<Item> items = new ArrayList<Item>();
public void addItem(Item item){
items.add(item);
}
public float getCost(){
float cost = 0.0f;
for (Item item : items) {
cost += item.price();
}
return cost;
}
public void showItems(){
for (Item item : items) {
System.out.print("Item : "+item.name());
System.out.print(", Packing : "+item.packing().pack());
System.out.println(", Price : "+item.price());
}
}
}
class MealBuilder {
public Meal prepareVegMeal (){
Meal meal = new Meal();
meal.addItem(new VegBurger());
meal.addItem(new Coke());
return meal;
}
public Meal prepareNonVegMeal (){
Meal meal = new Meal();
meal.addItem(new ChickenBurger());
meal.addItem(new Pepsi());
return meal;
}
}
◆应用场景:
◆建造者与抽象工厂模式的比较: