java 向上、向下取整，四舍五入

// 四舍五入long round = Math.round(2.499);System.out.println(round);long round2 = Math.round(3.5);System.out.println(round2);// 向上取整int res = (int)Math.ceil(3.1);System.out.println(res);// 向下取整
System.out.println((int)Math.floor(1.6));