math类
abs 绝对值 public static double abs(double a)
System.out.println(Math.abs(-10.4)); //10.4
System.out.println(Math.abs(10.1)); //10.1
ceil 返回大的值
System.out.println(Math.ceil(-10.1)); //-10.0
System.out.println(Math.ceil(10.7)); //11.0
System.out.println(Math.ceil(-0.7)); //-0.0
System.out.println(Math.ceil(0.0)); //0.0
System.out.println(Math.ceil(-0.0)); //-0.0
floor地板的意思，就是返回小的值
System.out.println(Math.floor(-10.1)); //-11.0
System.out.println(Math.floor(10.7)); //10.0
System.out.println(Math.floor(-0.7)); //-1.0
System.out.println(Math.floor(0.0)); //0.0
System.out.println(Math.floor(-0.0)); //-0.0
max 两个中返回大的值,min两个中小的值
System.out.println(Math.max(-10.1, -10)); //-10.0
System.out.println(Math.max(10.7, 10)); //10.7
System.out.println(Math.max(0.0, -0.0)); //0.0
random 取得一个大于或者等于0.0小于不等于1.0的随机数
System.out.println(Math.random()); //0.08417657924317234
System.out.println(Math.random()); //0.43527904004403717
rint 四舍五入，返回double值 （注意.5的时候会取偶数）
System.out.println(Math.rint(10.1)); //10.0
System.out.println(Math.rint(10.7)); //11.0
System.out.println(Math.rint(11.5)); //12.0
System.out.println(Math.rint(10.5)); //10.0
System.out.println(Math.rint(10.51)); //11.0
System.out.println(Math.rint(-10.5)); //-10.0
System.out.println(Math.rint(-11.5)); //-12.0
System.out.println(Math.rint(-10.51)); //-11.0
System.out.println(Math.rint(-10.6)); //-11.0
System.out.println(Math.rint(-10.2)); //-10.0
round 四舍五入，float时返回int值，double时返回long值
System.out.println(Math.round(10.1)); //10
System.out.println(Math.round(10.7)); //11
System.out.println(Math.round(10.5)); //11
System.out.println(Math.round(10.51)); //11
System.out.println(Math.round(-10.5)); //-10
System.out.println(Math.round(-10.51)); //-11
System.out.println(Math.round(-10.6)); //-11
System.out.println(Math.round(-10.2)); //-10
Math.sqrt 求开方
Math.sin 正弦函数
Math.asin 反正弦函数
Math.cos 余弦函数
Math.acos 反余弦函数
Math.tan 正切函数
Math.atan 反正切函数
Math.atan2 商的反正切函数