java List 流操作

• map

// 将集合中额code去掉${},
List<String> fullExpCodeList = searchDataCodeList.stream().map(code -> code.replaceAll("[${}]", "")).collect(Collectors.toList());
// 然后转换成数组list
List<String[]> fullCodeList = fullExpCodeList.stream().map(code -> code.split("[.]")).filter(code -> code.length == 3).collect(Collectors.toList());
if(fullCodeList.isEmpty()){
  return subjectDataMap;
}
// 获取访视信息List
List<String[]> phaseInfoList = fullCodeList.stream().map(code -> code[0].split("#")).distinct().collect(Collectors.toList());
// 获取form信息List
List<String[]> formInfoList = fullCodeList.stream().map(code -> code[1].split("#")).distinct().collect(Collectors.toList());
// 获取item信息List
List<String[]> itemInfoList = fullCodeList.stream().map(code -> code[2].split("#")).distinct().collect(Collectors.toList());
// 获取访视code list
List<String> phaseCodeList = phaseInfoList.stream().map(code -> code[0]).distinct().collect(Collectors.toList());
// 获取访视num list
List<String> phaseNumList = phaseInfoList.stream().map(code -> code[1]).distinct().collect(Collectors.toList());
// 获取form code list
List<String> formCodeList = formInfoList.stream().map(code -> code[0]).distinct().collect(Collectors.toList());

• 最大1

 List<String> dateList = new ArrayList<String>();
 dateList.add("2020-12-21 14:39:27");
 dateList.add("2020-12-22 14:39:27");
 dateList.add("2020-12-24 14:39:27");
 dateList.add("2020-12-25 14:39:36");
 dateList.add("2020-12-19 14:39:36");
 dateList.add("2020-12-24 14:39:36");
 Optional<String> dispatchDate = dateList.stream().max((a,b)->a.compareTo(b));
 //Optional<String> dispatchDate = dispathDateList.stream().max(Comparator.naturalOrder());
 System.out.println(dispatchDate.get());

• 最大2

 List<Item> itemList = new ArrayList<>();
 itemList.add(new Item(1, 10));
 itemList.add(new Item(0, 10));
 itemList.add(new Item(0, 20));
 itemList.add(new Item(0, 40));
 itemList.add(new Item(3, 10));
 itemList.add(new Item(0, 30));
 itemList.add(new Item(0, 50));
 itemList.add(new Item(2, 10));
 Optional<Item> itemOptional = itemList.stream().max(Comparator.comparing(Item::getA));