高效 告别996，开启java高效编程之门 2-7实战：判断逻辑参数化-匿名类

1.1　　重点

1.2　　代码编程

 

1.1　　重点

使用了匿名内部类，但是关于内存泄漏风险的解决一直没有明显的方案

1.2　　代码编程

商品实体类：（同2-3）

枚举类：（同2-3）

商品服务类：

package com.imooc.zhangxiaoxi.lambda.cart;

import java.util.ArrayList;
import java.util.List; public class CartService { /** * 匿名内部类，有内存泄漏的风险，不在生产项目中引用，只是为了后边引用出来lambda表达式 */ private static List<Sku> skuList = new ArrayList<Sku>(){ { add(new Sku(2020001,"无人机",999.00,1,999.00,SkuCategoryEnum.ELECTRONICS)); add(new Sku(2020002,"T-shirt",50.00,2,100.00,SkuCategoryEnum.CLOTHING)); add(new Sku(2020003,"人生的枷锁",30.00,1,30.00,SkuCategoryEnum.BOOKS)); add(new Sku(2020004,"老人与海",20.00,1,20.00,SkuCategoryEnum.BOOKS)); add(new Sku(2020005,"剑指高效编程",288.00,1,288.00,SkuCategoryEnum.BOOKS)); add(new Sku(2020006,"大头皮鞋",300.00,1,300.00,SkuCategoryEnum.CLOTHING)); add(new Sku(2020007,"杠铃",2000.00,1,2000.00,SkuCategoryEnum.SPROTS)); add(new Sku(2020008,"ThinkPad",5000.00,1,5000.00,SkuCategoryEnum.ELECTRONICS)); } }; public static List<Sku> getSkuList(){ return skuList; } /** * versionTestA * 找出购物车中所有电子产品 * * 注意for 循环 * for (Sku sku: skuList) 的使用 * @return */ public static List<Sku> getElectronicsSkuList(List<Sku> skuList){ List<Sku> lElectronicsList = new ArrayList<Sku>(); for (Sku sku: skuList){ if (sku.getSkuCategory().equals(SkuCategoryEnum.ELECTRONICS)){ lElectronicsList.add(sku); } } /* for (int i=0;i<skuList.size();i++){ if (skuList.get(i).getSkuCategory().equals(SkuCategoryEnum.ELECTRONICS)){ lElectronicsList.add(skuList.get(i)); } } */ return lElectronicsList; } /** * versionTestB * 单一维度条件参数化,传入不同的enum，打印出不同的产品列表 * * 注意第二个参数：如何调取枚举类参数 * * * @param skuList * @return */ public static List<Sku> filterSkuListByParam(List<Sku> skuList,SkuCategoryEnum skuCategoryEnum){ List<Sku> lElectronicsList = new ArrayList<Sku>(); for (int i=0;i<skuList.size();i++){ if (skuList.get(i).getSkuCategory().equals(skuCategoryEnum)){ lElectronicsList.add(skuList.get(i)); } } return lElectronicsList; } /** * versionTestC * 然并卵 * * 一个方法 可以 根据两个参数 任一参数判断， * * 若flag为true ，根据枚举类判断，否则，根据总价判断 * * @param skuList * @return */ public static List<Sku> filterSkuListByParamB(List<Sku> skuList,SkuCategoryEnum skuCategoryEnum,Double dTotalPrice,boolean flag){ List<Sku> lElectronicsList = new ArrayList<Sku>(); for (int i=0;i<skuList.size();i++){ if ((flag && skuList.get(i).getSkuCategory().equals(skuCategoryEnum)) || (!flag&&skuList.get(i).getTotalPrice()>dTotalPrice)){ lElectronicsList.add(skuList.get(i)); } } return lElectronicsList; } /** * versionTestD * 生产上不建议这种写法，会引起类爆炸。一切都是为了引入lambda表达式 * * @param skuList * @return */ public static List<Sku> filterSkuListByParamPrediCate(List<Sku> skuList,SkuPrediCate skuPrediCate){ List<Sku> lElectronicsList = new ArrayList<Sku>(); for (int i=0;i<skuList.size();i++){ if (skuPrediCate.test(skuList.get(i))){ lElectronicsList.add(skuList.get(i)); } } return lElectronicsList; } }

谓词接口：

package com.imooc.zhangxiaoxi.lambda.cart;

/**
 * 谓词接口
 */
public interface SkuPrediCate { boolean test(Sku sku); }

测试类：

package com.imooc.zhangxiaoxi.lambda.cart;

import com.alibaba.fastjson.JSON;
import org.junit.Test;

import java.util.List;

public class VersionTestE {

    @Test
   public void filterSkuListByParam(){
       List<Sku> skuList = CartService.getSkuList();

        /**
         * 使用匿名内部类 查询 总价 大于1000的
         */
        List<Sku> getParamSkuList = CartService.filterSkuListByParamPrediCate(skuList, new SkuPrediCate() {
            @Override
            public boolean test(Sku sku) {
                return sku.getTotalPrice() > 1000;
            }
        });
        System.out.println(JSON.toJSONString(getParamSkuList,true));
    }

}

打印日志：

[
    {
        "skuCategory":"SPROTS",
        "skuId":2020007,
        "skuName":"杠铃",
        "skuPrice":2000.0,
        "totalNum":1,
        "totalPrice":2000.0
    },
    {
        "skuCategory":"ELECTRONICS",
        "skuId":2020008,
        "skuName":"ThinkPad",
        "skuPrice":5000.0,
        "totalNum":1,
        "totalPrice":5000.0
    }
]

Process finished with exit code 0