Printing strings from an array in random order (java)

Question

I have this assignement for school for whitch i have to make a small program that will ask you a question, list the possible answers and you have to input the number of the answer. It would not be that much of a problem if not for two things:

-the answers have to show in different order every time the question is asked

-the teacher gave us a specific class/methode structure we have to follow

input/output
"logic" class with:
- constructor (String question, String[] answers, int indexOfTheCorrectAnswer)
- public String getQuestion
- public String[] getAnswers
- public String getCorrectAnswer
- public boolean controlAnswer
- private void randomize

Could you guys hint me a way to do the randomizing? The rest isnt that much of a problem to handle

For future questions be sure to leave the bit about "school" and "assignment" out of the questions as it can easily make questions targets of down votes and critisizm :) — Clyde D'Cruz, Mar 12 '15 at 18:04

score 1 · Answer 1 · answered Mar 12 '15 at 18:03

1

Collections have shuffle methods, so make an ArraList from your own Test class.

answered Mar 12 '15 at 18:03

Laszlo Lugosi

3,669
1
21
17

I think your answer is confusingly worded: `Collections` has a `shuffle` method, but `Collection`s do not have such a method. – Andy Turner Mar 12 '15 at 18:06
ahh didn't saw this before posting the answer. – Sameer Sawla Mar 12 '15 at 18:10

score 1 · Accepted Answer · answered Mar 12 '15 at 18:09

templated Collections.shuffle is the method that you could use.

Actually you should go with this only as it was specifically designed for that. Underlying is the fairly optimized shuffle algorithm. Though you can customize the algorithm by overriding specific methods.

http://www.tutorialspoint.com/java/util/collections_shuffle.htm This is an example that you can refer which shuffles the list.

Hope that helps.

score 0 · Answer 3 · answered Mar 12 '15 at 18:05

Look at java.util.Random for random number generation.

Random rnd = new Random(new Date().getTime());

The newDate() part seeds the random number generator so it won't have the exact same values every time you run your program.

I would then do the following:

In my class, make a pointer to the right answer before randomizing.
Copy the answers into an ArrayList.
Then do a loop. While there are still contents in the array from #2, generate a random number 0 <= rnd < count and use that as an index in that array to copy the value into a new array.

You now have the answers randomized.

kwikness · Answer 4 · 2015-03-12T18:34:21.390

0

String[] answers = new String[5];

//assume your array gets populated here...

//convert to a List so we can use Collections.shuffle()
List<String> answersList = Arrays.asList(answers);
Collections.shuffle(answersList);

//converting back to an array (although I'd avoid working with arrays alltogether if possible)
String[] shuffledAnswers = answersList.toArray(answers);

edited Mar 12 '15 at 18:34

answered Mar 12 '15 at 18:09

kwikness

1,425
4
21
37

Nice. good u are using shuffle as well. – Sameer Sawla Mar 12 '15 at 18:10
1

You could just use answersList.toArray(answers); instead of assign the result to a new array – dragon66 Mar 12 '15 at 18:26
Thanks, i tried to use your code and changed what i though i had to change to names of my own variables but i couldnt get it to work. But i snooped around the google and figured out how to make those array lists and stuff and this is what i ended up with ArrayList antwoordenList = new ArrayList(Arrays.asList(antwoorden)); Collections.shuffle(antwoordenList); shuffledAntwoorden = antwoordenList.toArray(shuffledAntwoorden); return; – Karol Rafalski Mar 13 '15 at 10:44

Printing strings from an array in random order (java)

4 Answers4