没有重复的随机数组

Question

我必须创建 15 个问题，其中只有 10 个随机显示。（10 个数组超过 15 个数组）。我需要确保在随机过程中没有重复数组。

public static void main(String() args){
   String question_1 = question_One();
   //to question 15
   String question_15 = question_fifteen();
   String [] question = new String [14]; 
   question[0] = question_1;
   question[1] = question_2;
   //to question 15
   question[14] = question_15;
   int random = (int) (Math.random()*11);
       System.out.print(question[random]);
}

Answer 1

我会采用一系列问题，将其打乱，然后只采用前十个问题。但是，Java 中的数组非常有限，使用适当的 Collection 会容易得多，例如 ArrayList:

// Build the question list:
List<String> questions = new ArrayList<>(15);
questions.add(question_1);
questions.add(question_2);
// etc...

// Shuffle it:
Collections.shuffle(questions);

// Ask the first ten:
List<String> questionsToAsk = questions.subList(0, 10);

编辑：
ArrayLists 和 Collections 的使用只是为了方便。同样的逻辑也适用于数组，尽管它需要你自己实现其中的一些：

// Build the question list:
String[] questions = new String[15];
questions[0] = question_1;
questions[1] = question_2;
// etc...

// Shuffle the first 10 elements.
// Although the elements can be taken from indexes above 10,
// there no need to continue shuffling these indexes.
Random r = new Random();
for (int i = 0; i < 10; ++i) {
    int swapIndex = r.nextInt(15 - i) + i;
    String temp = questions[i];
    questions[i] = questions[swapIndex];
    questions[swapIndex] = temp;

// Ask the first ten:
String[] questionsToAsk = new String[10];
for (int i = 0; i < 10; ++i) {
    questionsToAsk[i] = questions[i];
}

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