package com.arithmetic;import java.util.Arrays;public class StdRandom {// 随机返回【a,b)之间的一个 double 值public static double uniform(double a, double b) {return a + random() * (b-a);}// 随机返回【0..N)之间的一个 int 值public static int uniform(int N) {return (int)(random() * N);}// 随机返回 【start,end）之间的 int 值public static int uniform(int start, int end) {return start + uniform(end - start);}// 返回 0 ~ 1的随机值public static double random() {return Math.random();}// 随机将double数组中的元素排序public static void shuffle(double[] a) {for (int i = 0; i < a.length; i++) {// 将 a[i] 和 a[i...N-1]中任意一个元素交换int r = uniform(i,a.length);double temp = a[i];a[i] = a[r];a[r] = temp;}}public static void main(String[] args) {double[] a = {1,2,3,4,5,6,7};for (int i = 0; i < 30; i++) {System.out.println("随机返回【2,5）之间的 int 值 " + uniform(2,5));System.out.println("随机返回【0..5) 之间的一个 int 值 " + uniform(5));for (int k = 0; k < a.length; k++) {System.out.print(a[k]);}shuffle(a);System.out.println("随机排序后 : " + Arrays.toString(a));}}
}