一、Math类
1、概述
- Math 类包含了基本数学运算的方法,如:指数、对数、平方根、三角函数等
2、Math的成员方法
public static int abs(int a)
public static double ceil(double a)
public static double floor(double a)
public static int max(int a,int b)
public static double pow(double a,double b)
public static double random()
public static int round(float a)
public static double sqrt(double a)
package yunsuan; public class MathDemo { public static void main(String[] args){ System.out.println(Math.PI);//输出π的值 System.out.println(Math.E); System.out.println(Math.abs(-10));//输出绝对值 System.out.println(Math.ceil(12.99));//向上取整 System.out.println(Math.ceil(12.01));//向上取整 System.out.println("----------------------------"); System.out.println(Math.floor(12.99));//向下取整 System.out.println(Math.floor(12.01));//向下取整 System.out.println(Math.max(12,19));//从两个数中找大的 System.out.println(Math.min(12,19));//从两个数中找小的 System.out.println(Math.pow(3,2));//3的2次方 System.out.println("++++++++++++++++++++++++++++"); System.out.println(Math.random());//0-1之间的随机数 System.out.println(Math.round(3.14));//四舍五入 System.out.println(Math.sqrt(4));//4的平方根 } }
3、案例
获取任意范围内的随机数
package yunsuan;
import java.util.Scanner;
public class MathDemo {
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
System.out.println("请输入开始数:");
int start = sc.nextInt();
System.out.println("请输入结束数:");
int end = sc.nextInt();
for (int i = 0; i < 3; i++){
int num = getRandom(start,end);
System.out.println("获取了一个"+start+"与"+end+"之间的随机数,数字为:"+num);
}
}
private static int getRandom(int start, int end) {
//int number = (int)(Math.random()*100) + 1;//这是0到100之间的随机数
int number = (int)(Math.random()*(end - start + 1)) + start;
return number;
}
}
二、Random类
1、概述
Random()
:产生一个随机数Math.random()
:能够返回带正号的double值,该值大于等于0.0且小于1.0
2、构造方法
public Random()
public Random(long seed)
3、成员方法
public int nextInt()
public int nextInt(int n)
package yunsuan; import java.util.Random; public class MathDemo { public static void main(String[] args){ Random r1 = new Random();//没有给值,返回当前时间的毫秒值 Random r2 = new Random(1); System.out.println(r1.nextInt(100)); System.out.println(r2.nextInt(100)); } }