Double

四舍五入并保留小数点后两位

double score = 24.2455;
BigDecimal round = new BigDecimal(score).setScale(2, RoundingMode.UP);
System.out.println(round.doubleValue());

Iterable

转List类型

Iterable<Teacher> teacherIterable = repository.findAll();
List<Teacher> teacherList = new ArrayList<>();
teacherIterable.forEach(teacherList::add);

Collections

单个对象转换成List

List<MyObject> = Collections.singletonList(myObject);

将列表转换成不可修改的容器

Collections.unmodifiableList(items)