向上取整用Math.ceil(double a)
向下取整用Math.floor(double a)
举例：
double a=35;
double b=20;
double c = a/b;
System.out.println("c===>"+c); //1.75
System.out.println("c===>"+Math.ceil(c)); //2.0
System.out.println(Math.floor(c)); //1.0
原文：http://www.cnblogs.com/chenlong-50954265/p/4972217.html