Stream流使用记录

List<Long> idTemp = list.stream().map(SysDept::getDeptId).collect(Collectors.toList());

Long[] deptIds = idTemp.toArray(new Long[idTemp.size()]);

Long[] ids = listDept.stream().map(SysDept::getDeptId).toArray(Long[]::new);

List<ExcelS> list = new ArrayList();

        list.add(new ExcelS(new BigDecimal(12),1));

        list.add(new ExcelS(new BigDecimal(12),1));

        list.add(new ExcelS(new BigDecimal(12),1));

        list.add(new ExcelS(new BigDecimal(12),1));

        list.add(new ExcelS(new BigDecimal(12),2));

        //计算总价格

        BigDecimal reduce = list.stream().map(x-> x.getPrice().multiply(new BigDecimal(x.getNum()))).reduce(BigDecimal.ZERO,BigDecimal::add);

        System.out.println("总价格-------》"+reduce);

String数组转long数组

Long[] longIds = Arrays.stream(ids).map(str -> Long.parseLong(str.trim())).toArray(Long[]::new);

计算总和

List<ExcelS> list = new ArrayList();

        list.add(new ExcelS(new BigDecimal(12),1));

        list.add(new ExcelS(new BigDecimal(12),1));

        list.add(new ExcelS(new BigDecimal(12),1));

        list.add(new ExcelS(new BigDecimal(12),1));

        list.add(new ExcelS(new BigDecimal(12),2));

        //计算总价格

        BigDecimal reduce = list.stream().map(x-> x.getPrice().multiply(new BigDecimal(x.getNum()))).reduce(BigDecimal.ZERO,BigDecimal::add);

        System.out.println("总价格-------》"+reduce);

stream简单使用

  List<Integer> list = new ArrayList();

        list.add(1);

        list.add(2);

        list.add(4);

        list.add(4);

        list.add(3);

        list.add(5);

        //只取前3条数据

        Stream limit = list.stream().limit(3);

        Iterator iterator = limit.iterator();

        while (iterator.hasNext()) {

            System.out.println(iterator.next());

        }

        //排序，默认的排序

        Stream sorted = list.stream().sorted();

        Iterator iterator1 = sorted.iterator();

        while (iterator1.hasNext()) {

            System.out.println("iterator1=====" + iterator1.next());

        }

        //删除前三个skip(3)

        Stream skip = list.stream().skip(3);

        Iterator iterator2 = skip.iterator();

        while (iterator2.hasNext()) {

            System.out.println("iterator2=====" + iterator2.next());

        }

        //获取list长度

        System.out.println("count=" + list.stream().count());

        //去除重复的

        Stream distinct = list.stream().distinct();

        Iterator iterator3 = distinct.iterator();

        while (iterator3.hasNext()) {

            System.out.println("iterator3=====" + iterator3.next());

        }

        //获取到流进行过滤出二的倍数，并放入到一个数组中

        List<Integer> newList2 = list.stream().filter(x -> x % 2 == 0).collect(Collectors.toList());

        System.out.println(newList2);

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stream流的简单使用_.toarray(long[]::new)-CSDN博客文章浏览阅读222次。stream流的简单使用 List list = new ArrayList(); list.add(1); list.add(2); list.add(4); list.add(4); list.add(3); list.add(5); //只取前3条数据 Stream limit = list.stream().limit(3); _.toarray(long[]::new)https://blog.csdn.net/weixin_46553523/article/details/116453648
stream流的简单使用_.toarray(long[]::new)-CSDN博客文章浏览阅读222次。stream流的简单使用 List list = new ArrayList(); list.add(1); list.add(2); list.add(4); list.add(4); list.add(3); list.add(5); //只取前3条数据 Stream limit = list.stream().limit(3); _.toarray(long[]::new)https://blog.csdn.net/weixin_46553523/article/details/116453648