java数学工具类Math

java.lang.Math类是数学相关的工具类,里面提供了大量的静态方法,完成与数学运算的操作.

public static double abs(double num):获取绝对值.

public static double ceil(double num):向上取整.

public static double floor(double num):向下取整.

public static long round(double num):四舍五入.

Math.PI代表圆周率

package xiaochenyan.top.Demo;

public class Main20{
    public static void main(String[] args) {
        double a = 31.2;
        double b = 31.9;
        double c = 31.0;
        //取绝对值
        System.out.println(Math.abs(-31));//32
        System.out.println("==========================================");

        //向上取整
        System.out.println(Math.ceil(a));//32
        System.out.println(Math.ceil(b));//32
        System.out.println(Math.ceil(c));//32
        //向下取整
        System.out.println("==========================================");
        System.out.println(Math.floor(a));//31
        System.out.println(Math.floor(b));//31
        System.out.println(Math.floor(c));//31

        System.out.println("==========================================");
        //四舍五入
        System.out.println(Math.round(a));//31
        System.out.println(Math.round(b));//32
        System.out.println(Math.round(c));//31

        System.out.println("==========================================");
        //圆周率
        System.out.println(Math.PI);//3.141592653589793

    }
}