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//1.获得日期
LocalDate localDate = LocalDate.now();
//输出 yyyy-mm-dd
System.out.println(localDate.toString());
//获取今天是今年的第几天
System.out.println(localDate.getDayOfYear());
//第几月
System.out.println(localDate.getMonthValue());
//第几天
System.out.println(localDate.getDayOfWeek().getValue());
//2.便利User
List<User> mapList = new ArrayList<>();
//添加数据
for (int i = 0; i < 10; i++) {
User user = new User();
user.setId((int) (Math.random()*100));
user.setName("name" + i);
mapList.add(user);
}
//根据id升序排序
mapList.sort((s1,s2)-> s1.getId().compareTo(s2.getId()));
//获取user对象里面的id返回到indexList里面
List<Integer> indexList = mapList.stream()
.map(User::getId).collect(Collectors.toList());
//copy对象
List<User> newMapList = mapList.stream()
.map(oldUser -> {
User newUser = new User();
BeanUtils.copyProperties(oldUser, newUser);
return newUser;
}).collect(Collectors.toList());
//数组转List
List<String> arrayToList = Arrays.asList("1","3","2","3");
List<String> delRepetList = new ArrayList();
for (int i = 0; i < 5; i++) {
delRepetList.add(String.valueOf(i/2));
}
//去重复
Set s = new HashSet(delRepetList);
delRepetList.clear();
delRepetList.addAll(s);