【设计模式03】 建造者模式

定义：
   将一个复杂的构建与其表示相分离，使得同样的构建过程可以创建不同的表示。具体点说，就是考虑用相同的原料制作出不同的东西出来。例如：快餐店里的食物都是那几样，汉堡、薯条、咖啡，牛奶等，但是能搭配出不同得套餐。

案例代码：
项目目录

|—builder-pattern
  |—pom.xml
  |—src
      |—main
          |—java
              |—org
                  |—peko
                      |—design
                          |—pattern
                              |—Builder.java
                              |—fast_food
                                  |—FastFood.java
                                  |—impl
                                      |—Burger.java
                                      |—Chips.java
                                      |—Coffee.java
                                      |—Milk.java
                              |—impl
                                  |—PackageImpl.java
                              |—Package.java
          |—resources
      |—test
          |—java
              |—org
                  |—peko
                      |—design
                          |—pattren
                              |—Test01.java

FastFood.java

package org.peko.design.pattern.fast_food;

import java.math.BigDecimal;

public interface FastFood {
    String food();
    BigDecimal price();
}

Burger.java

package org.peko.design.pattern.fast_food.impl;

import org.peko.design.pattern.fast_food.FastFood;

import java.math.BigDecimal;

public class Burger implements FastFood {
    @Override
    public String food() {
        return "汉堡";
    }

    @Override
    public BigDecimal price() {
        return new BigDecimal("10");
    }
}

Chips.java

package org.peko.design.pattern.fast_food.impl;

import org.peko.design.pattern.fast_food.FastFood;

import java.math.BigDecimal;

public class Chips implements FastFood {
    @Override
    public String food() {
        return "薯条";
    }

    @Override
    public BigDecimal price() {
        return new BigDecimal("5");
    }
}

Coffee.java

package org.peko.design.pattern.fast_food.impl;

import org.peko.design.pattern.fast_food.FastFood;

import java.math.BigDecimal;

public class Coffee implements FastFood {
    @Override
    public String food() {
        return "咖啡";
    }

    @Override
    public BigDecimal price() {
        return new BigDecimal("4");
    }
}

Milk.java

package org.peko.design.pattern.fast_food.impl;

import org.peko.design.pattern.fast_food.FastFood;

import java.math.BigDecimal;

public class Milk implements FastFood {
    @Override
    public String food() {
        return "鸡肉";
    }

    @Override
    public BigDecimal price() {
        return new BigDecimal("6");
    }
}

Package.java

package org.peko.design.pattern;

import org.peko.design.pattern.fast_food.FastFood;

public interface Package {
    Package addFood(FastFood fastFood);
    Package addDrink(FastFood fastFood);
    String getDetail();
}

PackageImpl.java

package org.peko.design.pattern.impl;

import org.peko.design.pattern.Package;
import org.peko.design.pattern.fast_food.FastFood;

import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;

public class PackageImpl implements Package {

    private final List list = new ArrayList<>();
    private String packageName;
    private BigDecimal cost = BigDecimal.ZERO;

    private PackageImpl() {
    }

    public PackageImpl(String packageName){
        this.packageName = packageName;
    }

    public Package addFood(FastFood fastFood){
        this.list.add(fastFood);
        this.cost = this.cost.add(fastFood.price());
        return this;
    }

    public Package addDrink(FastFood fastFood){
        this.list.add(fastFood);
        this.cost = this.cost.add(fastFood.price());
        return this;
    }


    @Override
    public String getDetail() {
        StringBuilder detail = new StringBuilder("rn-----------------------------------------rn" +
                "套餐名称："+ this.packageName + "rn" +
                "套餐价格："+ this.cost + "rn" +
                "套餐内容："+ "rn");

        for(FastFood fastFood: list){
            detail.append("  主食：").append(fastFood.food()).append(" 价格：").append(fastFood.price()).append("rn");
        }

        return detail.toString();
    }
}

Builder.java

package org.peko.design.pattern;

import org.peko.design.pattern.fast_food.impl.Burger;
import org.peko.design.pattern.fast_food.impl.Chips;
import org.peko.design.pattern.fast_food.impl.Coffee;
import org.peko.design.pattern.fast_food.impl.Milk;
import org.peko.design.pattern.impl.PackageImpl;

public class Builder {
    public Package PackageOne(){
        return new PackageImpl("套餐1")
                .addFood(new Burger())
                .addDrink(new Coffee());
    }

    public Package PackageTwo(){
        return new PackageImpl("套餐2")
                .addFood(new Chips())
                .addDrink(new Milk());
    }
}

Test01.java

package org.peko.design.pattren;

import org.junit.Test;
import org.peko.design.pattern.Builder;

public class Test01 {
    @Test
    public void test01(){
        Builder builder = new Builder();
        System.out.println(builder.PackageOne().getDetail());
        System.out.println(builder.PackageTwo().getDetail());
    }
}

运行结果

-----------------------------------------
套餐名称：套餐1
套餐价格：14
套餐内容：
  主食：汉堡 价格：10
  主食：咖啡 价格：4


-----------------------------------------
套餐名称：套餐2
套餐价格：11
套餐内容：
  主食：薯条 价格：5
  主食：鸡肉 价格：6