lambda表达式常用基础操作

朱雀 2021-12-24 01:01 224阅读 0赞

List<Goods> list = Arrays.asList(
                    new Goods(1, "苹果", 15),
                    new Goods(2, "香蕉", 20),
                    new Goods(3, "橘子", 10),
                    null,
                    new Goods(5,"",null));
            list.forEach(e-> System.out.println(e));
            System.out.println("*****************************");
            
            //过滤空数据
            list=list.stream().filter(Objects::nonNull).filter(p->Objects.nonNull(p.getPrice())).collect(Collectors.toList());
            list.forEach(e-> System.out.println(e));
            System.out.println("*****************************");
            
            //过滤、排序、限制返回数量
            List<Goods> collect = list.stream().filter(g -> g.getPrice() > 10).sorted((g2, g1) -> g1.getPrice() - g2.getPrice())
    //                .forEach(System.out::println);
                    .limit(1)
                    .collect(Collectors.toList());
            System.out.println(collect);
            System.out.println("****************************");
            
            //最大值最小值
            Goods goods = list.stream().max((p1, p2) -> p1.getPrice() - p2.getPrice()).get();
            System.out.println("max:"+goods);
            Goods min = list.stream().min((p1, p2) -> p1.getPrice() - p2.getPrice()).get();
            System.out.println("min:"+min);
            System.out.println("******************************");
            
            //把流转为数据
            String collect1 = list.stream().map(Goods::getName).collect(Collectors.joining("-"));
            System.out.println(collect1);
            System.out.println("******************************");
            
            //数据统计
            IntSummaryStatistics ss = list.stream().mapToInt(Goods::getPrice).summaryStatistics();
            System.out.println("sum:"+ss.getSum());
            System.out.println("avg:"+ss.getAverage());
            System.out.println("count:"+ss.getCount());
            System.out.println("max:"+ss.getMax());
            System.out.println("min:"+ss.getMin());