java【Stream】

过滤

按条件筛选： stream().filter(p-> 条件).collect(Collectors.toList());

public List<T> getList(){
    return this.getRepository().findAll().stream().filter(p->!p.isDeleted()).collect(Collectors.toList());
}

分组

按某一列分组：stream().collect( Collectors.groupingBy(对象::取某一列的值, Collectors.toList()));

Map<String, List<ProductFamily>> sum =list.stream().collect(
        Collectors.groupingBy(ProductFamily::getCode, Collectors.toList()));

取得某一行

只取某一列：stream().map(对象::取某一列的值).collect(Collectors.toList());

List<String> manageBUList=this.getList().stream().map(BusinessUnit::getManageBU).collect(Collectors.toList());

求和

BigDecimal

BigDecimal sum =list.stream().map(Payroll::getSalary).reduce(BigDecimal.ZERO,BigDecimal::add);

int

int  sum = list.stream().map(Payroll::getSalary).sum();

double

double   sum = list.stream().mapToDouble(Payroll::getSalary).sum();

持续更新中。。。