java常用類解析十一：Random類(Math.random())產生指定範圍的隨機數或字元

package mine.util.others;import java.util.Random;public class GetRandom {// 返回ch1和ch2之間(包括ch1,ch2)的任意一個字元,如果ch1 > ch2，返回'\0'public static char getRandomChar(char ch1, char ch2) {if (ch1 > ch2)return 0;// 下面兩種形式等價// return (char) (ch1 + new Random().nextDouble() * (ch2 - ch1 + 1));return (char) (ch1 + Math.random() * (ch2 - ch1 + 1));}// 返回a到b之間(包括a,b)的任意一個自然數,如果a > b || a < 0，返回-1public static int getRandomInt(int a, int b) {if (a > b || a < 0)return -1;// 下面兩種形式等價// return a + (int) (new Random().nextDouble() * (b - a + 1));return a + (int) (Math.random() * (b - a + 1));}}

 

package mine.util.others;public class TestGetRandom {public static void main(String[] args) {System.out.println("測試隨機產生字元：");for (int i = 1; i <= 100; i++) {System.out.print(GetRandom.getRandomChar('A', 'Z') + "  ");if (i % 10 == 0)System.out.println();}System.out.println("測試隨機產生自然數：");for (int i = 1; i <= 100; i++) {System.out.print(GetRandom.getRandomInt(0, 9) + "  ");if (i % 10 == 0)System.out.println();}}}