我用的java8

list to Map (java 8)

      Map<String, String> collect = caBankTypeService.listCaBankType(new CaBankType()).stream().collect(Collectors.toMap(CaBankType::getBankUuid, CaBankType::getBankCenterName));

分组, 计数

    Map<string long> result =  
            items.stream().collect(  
                    Collectors.groupingBy(  
                            Function.identity(), Collectors.counting()  
                    )  
            ); 

排序

   int arr[] = {1, 4, 2, 8, 5};
        Arrays.parallelSort(arr);
        for(int i : arr){
            System.out.print(i + " ");
        }

java 8 分区

  Map<Boolean, List<CaCustomerCard>> collect = caCustomerCards.stream().collect(Collectors.partitioningBy(t -> t.getId() == cardId));