一.Math类的使用方法
public class demo{ public static void main(String[] args){ double pi = Math.PI; //Math函数库 System.out.println(pi); } }
二.Number & Math方法
1.xxxValue方法 (将 Number 对象转换为xxx数据类型的值并返回。)
public class demo{ public static void main(String[] args){ Integer x = 5; System.out.println(x.byteValue()); //int 转换为xxx System.out.println(x.doubleValue()); System.out.println(x.floatValue()); System.out.println(x.intValue()); System.out.println(x.longValue()); System.out.println(x.shortValue()); } }
2.compareTo方法(将number对象与参数比较。)
public class demo{ public static void main(String[] args){ Integer x = 5; System.out.println(x.compareTo(6)); System.out.println(x.compareTo(5)); System.out.println(x.compareTo(4)); } }
3.equals(判断number对象是否与参数相等。)
public class demo{ public static void main(String[] args){ Integer x = 5; //整型 Integer y = 10;//整型 Integer z =5;//整型 Short a = 5; //短整型 System.out.println(x.equals(y)); System.out.println(x.equals(z)); System.out.println(x.equals(a)); } }
4.valueOf(返回一个 Number 对象指定的内置数据类型)
public class demo{ public static void main(String[] args){ //将数值9转换为整型 Integer x = Integer.valueOf(9); //将数据5转换成双精度 Double c = Double.valueOf(5);、 //将字符串5转换为双精度 Double d = Double.valueOf("5"); //将字符串80转换为浮点型 float a = Float.valueOf("80"); //"444"(16进制) --> 10进制数 Integer b = Integer.valueOf("444",16); System.out.println(x); System.out.println(c); System.out.println(a); System.out.println(b); System.out.println(d); } }
5.toString(以字符串形式返回值。)
public class demo{ public static void main(String[] args){ Integer x = 5; //x转换为字符串类型 System.out.println(x.toString()); //将12整型转换为字符串 System.out.println(Integer.toString(12)); } }
6.parseInt(将字符串解析为int类型。)
public class demo{ public static void main(String[] args){ //将字符型9转换为整型 int x = Integer.parseInt("9"); //将字符串5转换为双精度5 double c = Double.parseInt("5"); //将16进制的字符数转化为整型(10进制) int b = Integer.parseInt("444",16); System.out.println(x); System.out.println(c); System.out.println(b); } }
7.abs(返回参数的绝对值。)
public class demo{ public static void main(String[] args){ Integer a = -8; double d = -100; float f = -90; //返回对应的绝对值 System.out.println(Math.abs(a)); System.out.println(Math.abs(d)); System.out.println(Math.abs(f)); } }
8.ceil(返回大于等于( >= )给定参数的的最小整数，类型为双精度浮点型。)
9.floor(返回小于等于（<=）给定参数的最大整数 。)
public class demo{ public static void main(String[] args){ double d = 100.675; float f = -90; //向上取整 System.out.println(Math.ceil(d)); System.out.println(Math.ceil(f)); //向下取整 System.out.println(Math.floor(d)); System.out.println(Math.floor(f)); } }
10.rint(返回与参数最接近的整数。返回类型为double。)
功能:返回参数最接近的值，如果两边都接近，取偶数值
public class demo{ public static void main(String[] args){ double d = 100.675; double e = 100.500; double f = 100.200; //取接近值 System.out.println(Math.rint(d)); System.out.println(Math.rint(e)); System.out.print(Math.rint(f)); } }
11.round(它表示四舍五入)
public class demo{ public static void main(String[] args){ double d = 100.675; //101 double e = 100.500; //101 float f = 100; //100 float g = 90f; //90 System.out.println(Math.round(d)); System.out.println(Math.round(e)); System.out.println(Math.round(f)); System.out.println(Math.round(g)); } }
12.min(返回两个参数中的最小值。)
13.max(返回两个参数中的最大值。)
public class demo{ public static void main(String[] args){ int a = 4; int b = 7; System.out.println("a,b中的最大值:" + Math.max(a,b)); System.out.println("a,b中的最小值" + Math.min(a,b)); } }
14.exp(返回自然数底数e的参数次方。)
public class demo{ public static void main(String[] args){ double x = 45.0; double y = 30.0; //输出数学E的值 System.out.printf("e的值为%.4f%n",Math.E); //输出e的x次幂的值 System.out.printf("exp(%.3f)为%.3f%n",x,Math.exp(x)); } }
15.log(返回参数的自然数底数的对数值。)
public class demo{ public static void main(String[] args){ double x = Math.E; //log以e为底e的值 System.out.printf("exp(%.3f)为%.3f%n",x,Math.log(x)); } }
16.pow(返回第一个参数的第二个参数次方。)
public class demo{ public static void main(String[] args){ double x = 2; double y = 3; //x的y次幂 System.out.printf("exp(%.3f,%.3f)为%.3f%n",x,y,Math.pow(x,y)); } }
17.sqrt(求参数的算术平方根。)
public class demo{ public static void main(String[] args){ double x = 4; //x的开根号 System.out.printf("sqrt(%.3f)为%.3f%n",x,Math.sqrt(x)); } }
18.sin(求指定double类型参数的正弦值。)
public class demo{ public static void main(String[] args){ double degrees = 45.0; //角度 double radians = Math.toRadians(degrees); //转化为弧度 System.out.format("pi 的值为 %.4f%n", Math.PI); System.out.format("%.1f 度的正弦值为 %.4f%n", degrees, Math.sin(radians)); } }
