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Java常用基础类(四):Math

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1.简介

Java的Math类封装了很多与数学有关的属性和方法。

2.举例说明

private void mathMethod(){

/**
* Math.sqrt()//计算平方根
* Math.cbrt()//计算立方根
* Math.hypot(x,y)//计算 (x的平方+y的平方)的平方根
*/

Log.d("TAG","Math.sqrt(16)----:"+Math.sqrt(16));//4.0
Log.d("TAG","Math.cbrt(8)----:"+Math.cbrt(8));//2.0
Log.d("TAG","Math.hypot(3,4)----:"+Math.hypot(3,4));//5.0

/**
* Math.pow(a,b)//计算a的b次方
* Math.exp(x)//计算e^x的值
* */

Log.d("TAG","------------------------------------------");
Log.d("TAG","Math.pow(3,2)----:"+Math.pow(3,2));//9.0
Log.d("TAG","Math.exp(3)----:"+Math.exp(3));//20.085536923187668

/**
* Math.max();//计算最大值
* Math.min();//计算最小值
* */

Log.d("TAG","------------------------------------------");
Log.d("TAG","Math.max(2.3,4.5)----:"+Math.max(7,15));//15
Log.d("TAG","Math.min(2.3,4.5)----:"+Math.min(2.3,4.5));//2.3

/**
* Math.abs求绝对值
*/

Log.d("TAG","------------------------------------------");
Log.d("TAG","Math.abs(-10.4)----:"+Math.abs(-10.4));//10.4
Log.d("TAG","Math.abs(10.1)----:"+Math.abs(10.1));//10.1

/**
* Math.ceil天花板的意思,就是返回大的值
*/

Log.d("TAG","------------------------------------------");
Log.d("TAG","Math.ceil(-10.1)----:"+Math.ceil(-10.1));//-10.0
Log.d("TAG","Math.ceil(10.7)----:"+Math.ceil(10.7));//11.0
Log.d("TAG","Math.ceil(-0.7)----:"+Math.ceil(-0.7));//-0.0
Log.d("TAG","Math.ceil(0.0)----:"+Math.ceil(0.0));//0.0
Log.d("TAG","Math.ceil(-0.0)----:"+Math.ceil(-0.0));//-0.0
Log.d("TAG","Math.ceil(-1.7)----:"+Math.ceil(-1.7));//-1.0

/**
* Math.floor地板的意思,就是返回小的值
*/

Log.d("TAG","------------------------------------------");
Log.d("TAG","Math.floor(-10.1)----:"+Math.floor(-10.1));//-11.0
Log.d("TAG","Math.floor(10.7)----:"+Math.floor(10.7));//10.0
Log.d("TAG","Math.floor(-0.7)----:"+Math.floor(-0.7));//-1.0
Log.d("TAG","Math.floor(0.0)----:"+Math.floor(0.0));//0.0
Log.d("TAG","Math.floor(-0.0)----:"+Math.floor(-0.0));//-0.0

/**
* Math.random 取得一个大于或者等于0.0小于不等于1.0的随机数[0,1)
*/

Log.d("TAG","------------------------------------------");
Log.d("TAG","Math.random()----:"+Math.random());//输出[0,1)间的随机数 0.8979626325354049
Log.d("TAG","Math.random()*100----:"+Math.random()*100);//输出[0,100)间的随机数 32.783762836248144

/**
* Math.rint 四舍五入
* 返回double值
*/

Log.d("TAG","------------------------------------------");
Log.d("TAG","Math.rint(10.1)----:"+Math.rint(10.1));//10.0
Log.d("TAG","Math.rint(10.7)----:"+Math.rint(10.7));//11.0
Log.d("TAG","Math.rint(-10.5)----:"+Math.rint(-10.5));//-10.0
Log.d("TAG","Math.rint(-10.51)----:"+Math.rint(-10.51));//-11.0
Log.d("TAG","Math.rint(-10.2)----:"+Math.rint(-10.2));//-10.0
Log.d("TAG","Math.rint(9)----:"+Math.rint(9));//9.0


/**
* Math.round 四舍五入
* float时返回int值,double时返回long值
*/

Log.d("TAG","------------------------------------------");
Log.d("TAG","Math.round(10.1)----:"+Math.round(10.1));//10
Log.d("TAG","Math.round(10.7)----:"+Math.round(10.7));//11
Log.d("TAG","Math.round(-10.5)----:"+Math.round(-10.5));//-10
Log.d("TAG","Math.round(-10.51)----:"+Math.round(-10.51));//-11
Log.d("TAG","Math.round(-10.2)----:"+Math.round(-10.2));//-10
Log.d("TAG","Math.round(9)----:"+Math.round(9));//9

/**
* Math.nextUp(a) 返回比a大一点点的浮点数
* Math.nextDown(a) 返回比a小一点点的浮点数
* Math.nextAfter(a,b) 返回(a,b)或(b,a)间与a相邻的浮点数 b可以比a小
* */

Log.d("TAG","------------------------------------------");
Log.d("TAG","Math.nextUp(1.2)----:"+Math.nextUp(1.2));//1.2000000000000002
Log.d("TAG","Math.nextDown(1.2)----:"+Math.nextDown(1.2));//1.1999999999999997
Log.d("TAG","Math.nextAfter(1.2, 2.7)----:"+Math.nextAfter(1.2, 2.7));//1.2000000000000002
Log.d("TAG","Math.nextAfter(1.2, -1)----:"+Math.nextAfter(1.2, -1));//1.1999999999999997

}

结果:

Math.sqrt(16)—-:4.0
Math.cbrt(8)—-:2.0
Math.hypot(3,4)—-:5.0


Math.pow(3,2)—-:9.0
Math.exp(3)—-:20.085536923187668


Math.max(2.3,4.5)—-:15
Math.min(2.3,4.5)—-:2.3


Math.abs(-10.4)—-:10.4
Math.abs(10.1)—-:10.1


Math.ceil(-10.1)—-:-10.0
Math.ceil(10.7)—-:11.0
Math.ceil(-0.7)—-:-0.0
Math.ceil(0.0)—-:0.0
Math.ceil(-0.0)—-:-0.0
Math.ceil(-1.7)—-:-1.0


Math.floor(-10.1)—-:-11.0
Math.floor(10.7)—-:10.0
Math.floor(-0.7)—-:-1.0
Math.floor(0.0)—-:0.0
Math.floor(-0.0)—-:-0.0


Math.random()—-:0.8979626325354049
Math.random()*100—-:32.783762836248144


Math.rint(10.1)—-:10.0
Math.rint(10.7)—-:11.0
Math.rint(-10.5)—-:-10.0
Math.rint(-10.51)—-:-11.0
Math.rint(-10.2)—-:-10.0
Math.rint(9)—-:9.0


Math.round(10.1)—-:10
Math.round(10.7)—-:11
Math.round(-10.5)—-:-10
Math.round(-10.51)—-:-11
Math.round(-10.2)—-:-10
Math.round(9)—-:9


Math.nextUp(1.2)—-:1.2000000000000002
Math.nextDown(1.2)—-:1.1999999999999997
Math.nextAfter(1.2, 2.7)—-:1.2000000000000002
Math.nextAfter(1.2, -1)—-:1.1999999999999997


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