向上取整：Math.ceil(double a)

向下取整：Math.floor(double a)

四舍五入取整：Math.round(double a)

直接取整数：intValue()

    public static void main(String[] args) {
        Double number = 5.3;
        Double number1 = 5.8;
        //向上取整
        Double ceil = Math.ceil(number);
        System.out.println("向上取整:" + ceil);
        //向下取整
        Double floor = Math.floor(number);
        System.out.println("向下取整:" + floor);
        //四舍五入
        double round = Math.round(number);
        double round1 = Math.round(number1);
        System.out.println("四舍五入:" + round);
        System.out.println("四舍五入:" + round1);
        //直接取整数
        int intValue = number.intValue();
        System.out.println("直接取整数:" + intValue);
    }