// 根據id去重
List<Person> unique = appleList.stream().collect(
collectingAndThen(
toCollection(() -> new TreeSet<>(comparingLong(Apple::getId))), ArrayList::new)
);

// 查詢流中最大 最小值
Optional<Dish> maxDish = Dish.menu.stream().
collect(Collectors.maxBy(Comparator.comparing(Dish::getCalories)));
maxDish.ifPresent(System.out::println);

Optional<Dish> minDish = Dish.menu.stream().
collect(Collectors.minBy(Comparator.comparing(Dish::getCalories)));
minDish.ifPresent(System.out::println);

引自https://blog.csdn.net/lu930124/article/details/77595585

// 把物件本身當做value

public Map<Long, Account> getIdAccountMap(List<Account> accounts) {
return accounts.stream().collect(Collectors.toMap(Account::getId, account -> account));
}