Final class, all static methods
package com.gaowei_13;
/*
* Math class
* final class
* Member variables:
* public static final double PI
* public static final double E
* Member methods:
* public static int abs(int a): take the absolute value
* public static double ceil(double a): 向上取整
* public static double floor(double a): round down
* public static int max(int a,int b): maximum value
* public static int min(int a,int b): minimum value
* public static double pow(double a,double a):a的b次幂
* public static double random(): random number [0.0, 1.0]
* public static int round(float a): rounding//+0.5 first and then rounding down
* public static int sqrt(double a): returns the positive square root of double
*
*/
public class MathDemo1 {
public static void main(String[] args) {
System.out.println("PI:"+Math.PI);
System.out.println("E:"+Math.E);
//public static int abs(int a): take the absolute value
System.out.println(Math.abs(10));
System.out.println(Math.abs(-10));
//public static double ceil(double a)
System.out.println(Math.ceil(12.43)); //13.0
System.out.println(Math.ceil(12.56)); //13.0
//public static double floor(double a)
System.out.println(Math.floor(12.43)); //12.0
System.out.println(Math.floor(12.56)); //12.0
//public static int max(int a,int b)
System.out.println(Math.max(12,10)); //12
System.out.println(Math.max(12,56)); //56
//The maximum value of the three data
// nested invocation of the method
System.out.println(Math.max(Math.max(5, 90),56));
//The maximum value of the four data
System.out.println(Math.max(Math.max(5, 90),Math.max(23, 67)));
//public static double pow(double a,double a):a的b次幂
System.out.println(Math.pow(2, 3)); //8.0
//public static double random(): random number [0.0, 1.0]
System.out.println(Math.random());
System.out.println("random1-100:"+ ((int)(Math.random()*100)+1));
//public static int round(float a): rounding
System.out.println(Math.round(12.4f));
System.out.println(Math.round(12.6f));
//public static double sqrt(double a): returns the positive square root of double
System.out.println(Math.sqrt(4));
}
}
===================================
Interview questions:
package com.gaowei_13;
/*
* need:
* Design a method to obtain random numbers in any range
*
*
*/
public class MathDemo2 {
public static void main(String[] args) {
int start = 12;
int end = 30;
for(int x=0;x<100;x++) {
int randNum = getRandom(12,30);
System.out.println(randNum);
}
}
private static int getRandom(int start, int end) {
int a = (int)(Math.random()*(end-start+1))+start;
// 1--100
//int a = (int)(Math.random()*(100-1+1))+1;
return a;
}
}