I\'ve got two arrays of question and answers
String questions[] = {
\"Q1?\",
\"Q2?\",
\"Q3?\"};
String answers[] = {
\"A1?\",
\"A2?\",
\"A3?\"}
Create a class QuestionAndAnswer
and use an array of that class.
You can rather shuffle a new array which holds the indices. And then get the elements from both array from the first index.
List<Integer> indexArray = Arrays.asList(0, 1, 2);
Collections.shuffle(indexArray);
String question = questions[indexArray.get(0)];
String answer = answers[indexArray.get(0)];
Of course, creating a class
containing questions
and answers
would be a more OO way, as other answers suggest. That way, you would have to maintain just one List
or array
, as compared to 3 arrays
in the current approach.
Java Collections has a (surprisingly) simple solution to this problem: Collections.shuffle(Collection<?>, Random)
with a Random
seeded with same seed.
List<Integer> quests = Arrays.asList(1, 2, 3, 4, 5);
List<Integer> answers = Arrays.asList(10, 20, 30, 40, 50);
long seed = System.nanoTime();
Collections.shuffle(quests, new Random(seed));
Collections.shuffle(answers, new Random(seed));
System.out.println(quests);
System.out.println(answers);
Extra optimization is dangerous. This DOE NOT WORK:
long seed = System.nanoTime();
Random rnd = new Random(seed);
Collections.shuffle(quests, rnd);
Collections.shuffle(answers, rnd);
Originally posted at: https://stackoverflow.com/a/44863528/1506477
Creating a class for holding both the question and answer together would be an easier and more OO solution:
class QuestionAnswerPair {
private final String question;
private final String answer;
public QuestionAnswerPair(String question, String answer) {
this.question = question;
this.answer = answer;
}
}
And then:
QuestionAnswerPair[] questions = new QuestionAnswerPair[] {
// Put questions here
};
Collections.shuffle(Arrays.asList(questions));
Instead of shuffling answers and questions, you may shuffle an extra array of integers that has indexes to questions/answers and then extract question and answers from corresponding arrays using shuffled indexes.
Idea from: http://www.vogella.com/tutorials/JavaAlgorithmsShuffle/article.html
public static void shuffle2ArraysTogther(String[] a, String[] b) {
if(a.length == b.length) {
int n = a.length;
Random random = new Random();
random.nextInt();
for (int i = 0; i < n; i++) {
int change = i + random.nextInt(n - i);
swap(a, i, change);
swap(b, i, change);
}
}
}
private static void swap(String[] a, int i, int change) {
String helper = a[i];
a[i] = a[change];
a[change] = helper;
}
private static void swap(String[] a, int i, int change) {
String helper = a[i];
a[i] = a[change];
a[change] = helper;
}
String questions[] = {
"Q1?",
"Q2?",
"Q3?"
};
String answers[] = {
"A1?",
"A2?",
"A3?"
};
shuffle2ArraysTogther(questions, answers);
for (String i : questions) {
System.out.println(i);
}
for (String i : answers) {
System.out.println(i);
}