有没有办法让我从一个数组中随机生成字符串而不重复一个以上两次？答案

【问题标题】：Is there a way for me to randomly generate Strings from an array without duplicating one more than twice?有没有办法让我从一个数组中随机生成字符串而不重复一个以上两次？
【发布时间】：2017-11-15 01:34:59
【问题描述】：

目前正在制作一个程序，该程序将从两个不同的数组生成字符串列表，但现在它所做的只是重复生成字符串所需的次数，有时会重复生成多个字符串。

    public class ListGenerator
    {
          public static void main(String[] args)
          { 
           //number generator to determine which string to print
           Random generator = new Random();
           int rand;

           //counter to determine number of printed lines
           int counter = 0;

           //coin flip to say which array the string will come from
           Random coinFlip = new Random();
           int coin;

           String[] list1;
           list1 = new String[5]
           list1[0] = "Alpha"
           list1[1] = "Beta"
           list1[2] = "Charlie"
           list1[3] = "Delta"
           list1[4] = "Echo"

           String[] list2;
           list2 = new String[5]
           list2[0] = "Apple"
           list2[1] = "Pear"
           list2[2] = "Grape"
           list2[3] = "Banana"
           list2[4] = "Orange"

           for(counter = 0; counter < 15; counter++)
           {
                coin = coinFlip.nextInt(2)+1;

                if(coin == 1)
                {
                      rand = generator.nextInt(list1.length);
                      System.out.println(list1[rand]);
                }
                else if(coin == 2)
                {
                      rand = generator.nextInt(list2.length);
                      System.out.println(list2[rand]);
                }
           }
           }
    }

有没有办法让我在生成的 15 行中生成像“Apple”或“Beta”这样的字符串不超过两次？

预期输出：

    (1) Apple [printed first time]
    (2) Charlie [printed first time]
    (3) Pear [printed first time]
    (4) Beta [printed first time]
    (5) Apple [printed second time]
    (6) Echo [printed first time]
    (7) Banana [printed first time]
    (8) Banana [printed second time]
    (9) Echo [printed second time]
    (10) Alpha [printed first time]
    (11) Grape [printed first time]
    (12) Delta [printed first time]
    (13) Beta [printed second time]
    (14) Orange [printed first time]
    (15) Grape [printed second time]

其中 5 个字符串生成了两次但不超过两次，但在我的代码中，它可以生成任何字符串 3、4、5 等次。

我知道我的代码组织得不是最好或最有效的，我只需要关于这个重复问题的帮助

【问题讨论】：

顺便说一句，您在初始化过程中重复list2[0] 五次。

标签： java arrays math random duplicates

【解决方案1】：

创建一个包含 20 个值的新 ArrayList，将 list1 和 list2 中的每个值添加两次。

现在shuffle() 列表并取前 15 个值。

String[] list1 = { "Alpha", "Beta", "Charlie", "Delta", "Echo" };
String[] list2 = { "Apple", "Pear", "Grape", "Banana", "Orange" };

List<String> allTwice = new ArrayList<>(20);
allTwice.addAll(Arrays.asList(list1));
allTwice.addAll(Arrays.asList(list1));
allTwice.addAll(Arrays.asList(list2));
allTwice.addAll(Arrays.asList(list2));
Collections.shuffle(allTwice);
String[] result = allTwice.subList(0, 15).toArray(new String[15]);

for (String value : result)
    System.out.println(value);

示例输出

Alpha
Charlie
Echo
Apple
Grape
Delta
Apple
Echo
Grape
Banana
Orange
Orange
Pear
Charlie
Beta

【讨论】：