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:
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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