[Solved] Suggest data-structure for this use case [closed]

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Since you want the thread to wait for an answer, I’d suggest creating a question object that has the question text, can store the answer, and has a CountDownLatch for tracking when the answer is available.

public final class Question {
    private final String   question;
    private String         answer;
    private CountDownLatch latch = new CountDownLatch(1);

    public Question(String question) {
        this.question = question;
    }
    public String getQuestion() {
        return this.question;
    }
    public String getAnswer() throws InterruptedException {
        this.latch.await();
        return this.answer;
    }
    public void setAnswer(String answer) {
        this.answer = answer;
        this.latch.countDown();
    }
}

Your worker thread can then send that question to the main Queue, and wait for the answer, e.g.

public final class Worker implements Runnable {
    private final Queue<Question> queue;
    private final int             delayInSeconds;
    private final String[]        questions;

    public Worker(Queue<Question> queue, int delayInSeconds, String... questions) {
        this.queue = queue;
        this.delayInSeconds = delayInSeconds;
        this.questions = questions;
    }
    @Override
    public void run() {
        List<String> answers = new ArrayList<>();
        try {
            for (String question : this.questions) {
                Thread.sleep(this.delayInSeconds * 1000L);
                Question q = new Question(question);
                this.queue.add(q);
                String answer = q.getAnswer();
                answers.add(answer);
            }
        } catch (InterruptedException unused) {
            System.out.println("Interrupted");
        }
        System.out.println(answers);
    }
}

The main thread would then use some kind of BlockingQueue to wait for questions, and to process them one at a time, e.g. like this:

public static void main(String[] args) throws Exception {
    BlockingQueue<Question> queue = new LinkedBlockingQueue<>();
    Worker w1 = new Worker(queue, 3, "Can you play poker?",
                                     "Can you juggle?",
                                     "Can you summersault?");
    Worker w2 = new Worker(queue, 4, "How old are you?",
                                     "How tall are you?");
    new Thread(w1).start();
    new Thread(w2).start();
    Scanner in = new Scanner(System.in); 
    for (int i = 0; i < 5; i++) {
        Question q = queue.take();
        System.out.println(q.getQuestion());
        String answer = in.nextLine();
        q.setAnswer(answer);
    }
}

Sample output

Can you play poker?
yes
How old are you?
13
Can you juggle?
no
How tall are you?
5 11
Can you summersault?
[13, 5 11]
no
[yes, no, no]

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solved Suggest data-structure for this use case [closed]