package com.bage.study.java.random;

import java.util.Random;

public class RandomUtils {

public static void main(String[] args) {

int number = 30;

int min = 0;

int max = 30;

int randoms[] = getRandoms(number,min,max);

for (int i = 0; i < randoms.length; i++) {

if(i % 10 == 0) {

System.out.println("");

}

System.out.print(randoms[i] + "\t");

}

System.out.println("\n----------------------------------");

randoms = getRandoms(5,new int[] {1,2,3,4,5,6,7,8,9});

for (int i = 0; i < randoms.length; i++) {

if(i % 10 == 0) {

System.out.println();

}

System.out.print(randoms[i] + "\t");

}

}

/**

*

* @param number 随机数个数

* @param min 最小值[包含]

* @param max 最大值[包含]

* @return

*/

private static int[] getRandoms(int number, int min, int max) {

int n = max - min + 1;

int a[] = new int[n];

for (int i = 0; i < a.length; i++) {

a[i] = min + i ;

}

Random random = new Random();

int res[] = new int[number];

for (int i = 0; i < number; i++) {

int tempIndex = random.nextInt(n);

int temp = a[a.length - 1 - i];

a[a.length - 1 - i] = a[tempIndex];

a[tempIndex] = temp;

res[i] = a[a.length - 1 - i];

n -- ;

}

return res;

}

/**

*

* @param number 个数

* @param a 在a【】里面随机选择 number个

* @return

*/

private static int[] getRandoms(int number,int[] a) {

int n = a.length;

Random random = new Random();

int res[] = new int[number];

for (int i = 0; i < number; i++) {

int tempIndex = random.nextInt(n);

int temp = a[a.length - 1 - i];

a[a.length - 1 - i] = a[tempIndex];

a[tempIndex] = temp;

res[i] = a[a.length - 1 - i];

n -- ;

}

return res;

}

}