lambda表达式

//判断集合中元素的重复
List<User> distinctClass = recordsList.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(data -> data.getCustomerCode()))), ArrayList::new));
if(distinctClass.size()!=recordsList.size()) throw new ExcelImortException("1","编码不一致，只能存在一个编码",importResult.getList());

//判断集合中的元素是否存在值
List<User> recordsListNo = recordsList.stream().filter(data -> StringUtils.isNotBlank(data.getErrorMsg())).collect(Collectors.toList());
if(recordsListNo.size() > 0) throw new ExcelImortException("1","有异常数据，请修改完成后重新提交",importResult.getList());

List<User> recordsListYes = recordsList.stream().filter(data -> StringUtils.isEmpty(data.getErrorMsg())).collect(Collectors.toList());
if(recordsListYes.size()==0) throw new ExcelImortException("1","正常数据为空，请修改完成后重新提交",importResult.getList());

　　

detailList.forEach(item->{
	UserDetailBiz.insertSelective(item);
});

　

//分组并计算出现次数
Map<String, Long> customerAndCout = list.stream().
		collect(Collectors.groupingBy(OrderOutDetail::getCustomerName,Collectors.counting()));
//排序
Map<String, String> customerAndCoutMap  = new LinkedHashMap<>();
customerAndCout.entrySet().stream().sorted(Map.Entry.<String, Long>comparingByValue().reversed())
		.forEachOrdered(e -> customerAndCoutMap.put(e.getKey(), e.getValue().toString()));;
//循环赋值
for(String key : customerAndCoutMap.keySet()){
	c3=new Cell(new Paragraph(key+"： "+customerAndCoutMap.get(key),keyfont));
	tFoot.addCell(c3);
}