数学运算(素数质数整数浮点数判断/阶乘/byte数组转换为16进制/打印九九乘法表)

package 运算及类型转换类;import java.util.Date;import java.util.regex.Pattern;public class 数学运算 {/** * 判断任意一个整数是否素数 isPrimes *  * @param n * @return boolean */public static boolean 判断任意一个整数是否素数(int n) {for (int i = 2; i <= Math.sqrt(n); i++) {if (n % i == 0) {return false;}}return true;}/** * 获得任意一个整数的阶乘，递归 factorial *  * @param n * @return n! */public static int 获得任意一个整数的阶乘(int n) {if (n == 1) {return 1;}return n * 获得任意一个整数的阶乘(n - 1);}/** * 将指定byte数组以16进制的形式打印到控制台 printHexString *  * @param hint *            String * @param b *            byte[] * @return void */public static void 将指定byte数组以16进制的形式打印到控制台(byte[] b) {for (int i = 0; i < b.length; i++) {String hex = Integer.toHexString(b[i] & 0xFF);if (hex.length() == 1) {hex = '0' + hex;}System.out.print(hex.toUpperCase() + " ");}System.out.println("");}/** * 判断是否为质数 isPrime *  * @param x * @return */public static boolean 判断是否为质数(int x) {if (x <= 7) {if (x == 2 || x == 3 || x == 5 || x == 7)return true;}int c = 7;if (x % 2 == 0)return false;if (x % 3 == 0)return false;if (x % 5 == 0)return false;int end = (int) Math.sqrt(x);while (c <= end) {if (x % c == 0) {return false;}c += 4;if (x % c == 0) {return false;}c += 2;if (x % c == 0) {return false;}c += 4;if (x % c == 0) {return false;}c += 2;if (x % c == 0) {return false;}c += 4;if (x % c == 0) {return false;}c += 6;if (x % c == 0) {return false;}c += 2;if (x % c == 0) {return false;}c += 6;}return true;}/** * 判断是否为整数 isInteger *  * @param str 传入的字符串 * @return    是整数返回true,否则返回false */public static boolean 判断是否为整数(String str) {Pattern pattern = Pattern.compile("^[-\\+]?[\\d]*$");return pattern.matcher(str).matches();}/** * 判断是否为浮点数，包括double和float isDouble *  * @param str *            传入的字符串 * @return 是浮点数返回true,否则返回false */public static boolean 判断是否为浮点数(String str) {Pattern pattern = Pattern.compile("^[-\\+]?[.\\d]*$");return pattern.matcher(str).matches();}    /**     *一个for循环打印九九乘法表     *nineNineMultiTable    */     public void 打印九九乘法表()     {       for (int i = 1,j = 1; j <= 9; i++) {           System.out.print(i+"*"+j+"="+i*j+" ");           if(i==j)           {               i=0;               j++;               System.out.println();           }       }     } public static void main(String[] args) {System.out.println(获得任意一个整数的阶乘(4));}}