Math工具类

1、获取绝对值

public static double abs(double num);

double min=-10.8;
System.out.println(Math.abs(min));

2、

public static double ceil(double num);

double min=-10.8;
System.out.println(Math.ceil(min));

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3、向下取整

public static double floor(double num);

4、四舍五入

public static long round(double)

5、圆周率

Math.PI

注：
（1）给明一个范围要用for循环
double max=5.9;
int count=0;
for(int i = (int) Math.ceil(min); i<max; i++){

}

（2）复习：强制转换

int i = (int) min