設計模式之建造者模式

時間 2019-11-09

標籤設計模式建造者简体版

原文原文鏈接

1、定義

你有沒有出現過點了個外賣，結果外賣送過來的時候發現忘了點個米飯。結果只能屁顛屁顛再點一份米飯，再等一個小時。你有沒有經歷炒好了全部的菜以後，發現你尚未煮飯的尷尬？來看看建造者模式是怎麼來建立對象的。

定義（百度百科）：建造者模式是設計模式的一種，將一個複雜對象的構建與它的表示分離，使得一樣的構建過程能夠建立不一樣的表示。java

核心有兩點：設計模式

一、將建立對象的代碼，過程與對象分離。bash

二、可構建出不一樣的對象。ide

2、UML

如圖，定義了各類菜品，建造者模式相關的爲圖中框出來的部分，Meal套餐中能夠有各類菜品，真正去構建Meal的是在MealABuilder中去進行構建（實現了定義中核心點1，Meal與構建Meal代碼分離）。使用不一樣的建造器，構建出來的菜單是不同的（實現了定義中核心點2），Director是構建的指揮類，負責控制菜單對象的生成過程。測試

是否是看着還不太理解各種的做用？？別急，接着往下看例子.....ui

3、代碼實現

咱們來看下建立外賣訂單怎麼來抽象，並保證咱們的訂單必定預約了米飯。this

一、咱們先定義各類菜品及套餐類，假設能夠點的菜爲：米飯、紅燒魚、土豆、番茄炒雞蛋spa

package com.design.builder;

public abstract class Food {
    private String foodName;
    private int price;

    public Food(String foodName, int price) {
        this.foodName = foodName;
        this.price = price;
    }

    public String getFoodName() {
        return foodName;
    }
    public void setFoodName(String foodName) {
        this.foodName = foodName;
    }
    public int getPrice() {
        return price;
    }
    public void setPrice(int price) {
        this.price = price;
    }

    public void showTheFood(){
        System.out.println("食物："+foodName+"，價格："+price);
    }
}
複製代碼

package com.design.builder;

/**
 * 米飯
 */
public class Rice extends Food {
    public Rice() {
        super("米飯", 3);
    }
}
複製代碼

package com.design.builder;

public class Fish extends Food {
    public Fish() {
        super("紅燒魚", 20);
    }
}
複製代碼

package com.design.builder;

/**
 * 土豆
 */
public class Potato extends Food{

    public Potato() {
        super("土豆", 8);
    }
}
複製代碼

package com.design.builder;

/**
 * 番茄炒蛋
 */
public class TomatoWithEgg extends Food{

    public TomatoWithEgg() {
        super("番茄炒蛋", 15);
    }
}複製代碼

package com.design.builder;
/**
套餐類
*/
public class Meal {

    private Rice rice;

    private Fish fish;

    private Potato potato;

    private TomatoWithEgg tomatoWithEgg;

    public Rice getRice() {
        return rice;
    }

    public void setRice(Rice rice) {
        this.rice = rice;
    }

    public Fish getFish() {
        return fish;
    }

    public void setFish(Fish fish) {
        this.fish = fish;
    }

    public Potato getPotato() {
        return potato;
    }

    public void setPotato(Potato potato) {
        this.potato = potato;
    }

    public TomatoWithEgg getTomatoWithEgg() {
        return tomatoWithEgg;
    }

    public void setTomatoWithEgg(TomatoWithEgg tomatoWithEgg) {
        this.tomatoWithEgg = tomatoWithEgg;
    }

    public void showMeal(){
        System.out.println("=========套餐===========");
        if (rice != null){
            rice.showTheFood();
        }
        if(fish != null){
            fish.showTheFood();
        }
        if(potato != null){
            potato.showTheFood();
        }
        if(tomatoWithEgg != null){
            tomatoWithEgg.showTheFood();
        }
        System.out.println("========套餐結束=========");

    }
}
複製代碼

二、構建類，即建立套餐的類，在定義中，咱們知道對象的建立是與對象分離的。因而咱們就在該構建類中來定義套餐對象。設計

1）、先定義接口，構建類中，咱們定義了增長米飯，增長菜的方法。3d

package com.design.builder;
//構造者抽象類
public interface IBuilder {
    //給套餐增長米飯
    public void addRice();
    //給套餐增長菜
    public void addFood();
    public Meal build();
}

複製代碼

2）、構建類

package com.design.builder;

/**
 * 套餐A建造者
 */
public class MealABuilder implements IBuilder{

    private Meal meal;

    public MealABuilder() {
        meal = new Meal();
    }

    @Override
    public void addRice(){
        meal.setRice(new Rice());
    }

    //點菜的方法
    @Override
    public void addFood() {
        //套餐A，紅燒魚，爆炒土豆
        meal.setPotato(new Potato());
        meal.setFish(new Fish());
    }

    @Override
    public Meal build(){
        return meal;
    }
}

複製代碼

package com.design.builder;

/**
 * 套餐B建造者
 */
public class MealBBuilder implements IBuilder {

    private Meal meal;

    public MealBBuilder() {
        meal = new Meal();
    }

    @Override
    public void addRice() {
        meal.setRice(new Rice());
    }

    //點菜的方法
    @Override
    public void addFood() {
        //套餐B，西紅柿炒雞蛋，紅燒魚
        meal.setTomatoWithEgg(new TomatoWithEgg());
        meal.setFish(new Fish());
    }

    @Override
    public Meal build() {
        return meal;
    }
}複製代碼

三、指揮類，用來定義構建的過程，套餐構建爲：增長米飯，增長菜。

package com.design.builder;

public class Director {

    private IBuilder mealBuilder;

    public Director(IBuilder mealBuilder){
        this.mealBuilder = mealBuilder;
    }

    /**
     * 構建套餐
     */
    public void buildMeal(){
        mealBuilder.addRice();
        mealBuilder.addFood();
    }

}

複製代碼

四、測試

package com.design.builder;

import javafx.util.Builder;

public class TestMain {

    public static void main(String[] args) {
        MealBuilder builder = new MealBuilder();
        Director director = new Director(builder);
        director.buildMealA();
        builder.build().showMeal();

        MealBuilder builder2 = new MealBuilder();
        Director director2 = new Director(builder2);
        director2.buildMealB();
        builder2.build().showMeal();
    }
}
複製代碼

執行結果