定义元素类型为int、元素个数不受限制的集合类Set，包括：<=（包含于）、==（相等）、!=（不等）、 |（并集）、 &（交集）、-（差集）、+=（增加元素）、-=（删除元素）等操作（38）-Defined element type is int, the number of unrestricted elements in a collection of class Set, including: " = (equal ),!=( included in ),==( range), | (and set), &　(intersection),- (difference sets ),+=( increasing element ),-=( remove elements) and other operations (38)