JAVA--HashSet实现不重复随机数

直接贴代码

import java.util.ArrayList;
import java.util.HashSet;

public class HashSet_Test {
    public static void main(String[] args) {
        //使用HashSet，新建不重复的随机数组
        long tstr = System.currentTimeMillis();
        HashSet<Integer> hashSet_numbers = new HashSet<Integer>();
        while(hashSet_numbers.size() < 50){
            int i = (int)(Math.random()*100);
            hashSet_numbers.add(i);
        }

        long tend = System.currentTimeMillis();

        for (int i : hashSet_numbers) {
            System.out.print(i + "\t");
        }
        System.out.println();
        //HashSet也可以直接打印
        System.out.println("UseTime:" + (tend - tstr));

        //使用arrayList实现不同的随机数集合
        long tstr1 = System.currentTimeMillis();
        ArrayList<Integer> alTest= new ArrayList<>();
        while (alTest.size() < 50){
            int j = (int)(Math.random()*100);
            if(! alTest.contains(j))
                alTest.add(j);
        }
        long tend1 = System.currentTimeMillis();
        System.out.println(alTest);
        System.out.println("UseTime:" + (tend1 - tstr1));
    }

}

结果

0	1	2	3	5	6	8	13	14	15	23	24	25	29	31	34	35	36	37	48	50	51	52	53	57	58	59	60	63	64	65	66	69	70	72	73	74	76	78	81	82	86	87	89	92	93	94	97	98	99	
UseTime:2
[56, 24, 44, 83, 12, 69, 68, 96, 59, 66, 67, 6, 76, 77, 75, 3, 87, 26, 14, 51, 36, 40, 35, 70, 95, 48, 19, 58, 81, 63, 55, 78, 13, 7, 94, 17, 4, 46, 31, 25, 60, 2, 85, 34, 93, 80, 45, 54, 0, 98]
UseTime:1