Math类呕心整理和BigDecimal的完美展示

Math类呕心整理和BigDecimal的完美展示

Math：里面的字段，和方法都是静态的，直接使用类名调用即可

//字段double pi = Math.PI;System.out.println(pi);double e = Math.E;System.out.println(e);//方法double random = Math.random();  //获取随机的小数   0<=小数<1;/*    public static int abs ( int a)取绝对值public static double ceil ( double a)向上取整public static double floor ( double a)向下取整public static int max ( int a, int b)获取最大值public static int min ( int a, int b)获取最小值public static double pow ( double a, double b)获取a的b次幂*/System.out.println(Math.abs(-1));System.out.il(3.14));System.out.println(Math.floor(3.14));System.out.und(3.59));System.out.println(Math.max(30, 100));System.out.println(Math.max(Math.max(30, 100),699));System.out.println(Math.pow(2, 3));System.out.println(Math.sqrt(4));double pow = Math.pow(8, 1/3.0);System.out.println(pow);// static double cos ( double a)返回角的三角余弦。double cos = s(Math.PI / 3.0);System.out.println(cos);

BigDecimal的完美展示

double a=10;double b=3;System.out.println(a/b);*/构造方法public BigDecimal(String val)成员方法public BigDecimal add (BigDecimal augend)//加public BigDecimal subtract (BigDecimal subtrahend)//减public BigDecimal multiply (BigDecimal multiplicand)//乘public BigDecimal divide (BigDecimal divisor)//除法public BigDecimal divide (BigDecimal divisor,int scale, int roundingMode)//scale 小数点后面保留几位// roundingMode 取舍模式 比如四舍五入*/BigDecimal a = new BigDecimal("3.1444444444444");BigDecimal b = new BigDecimal("3.14444444444444444422222222");//System.out.println(3.1444444444444* 3.14444444444444444422222222);BigDecimal multiply = a.multiply(b);System.out.println(multiply);BigDecimal a1 = new BigDecimal("10");BigDecimal b1 = new BigDecimal("3");//如果不能整除，你得决定保留 多少位，然后再规定取舍模式BigDecimal divide = a1.divide(b1, 30, BigDecimal.ROUND_HALF_UP);System.out.println(divide);System.out.println(10.0 / 3.0);System.out.println(1 == 0.99999999999999999999999999999999999999999999999999999999999999);