CODEWITHSUNDEEP
javarandom
walter
walter

Reputation: 309

Getting elegant dataset from the random values from collection

I need to get dataset from values (prepared set) when every value should appear at least once on random positions.

After running the following code this condition satisfied only sometimes. How is possible to improve the generation?

private static Random rand = new Random();
    private static int N = 5;

    public static void main(String[] args){
        List<String> indexList = new ArrayList<>();
        indexList.add("aaa");
        indexList.add("bbb");
        indexList.add("ccc");
        indexList.add("ddd");


        List<String> generatedDataList = new ArrayList<String>();

        for (int i=0; i<=5; i++) {
            String generatedIndex = getRandomValue(indexList);
            System.out.println("Step " + i+ ": " + generatedIndex);
            generatedDataList.add(generatedIndex);
        }

        }


    static  String getRandomValue(List<String> list){
          return list.get(rand.nextInt(list.size()));
    }

Upvotes: 0

Views: 37

Answers (2)

Paul Boddington
Paul Boddington

Reputation: 37645

If you want every string to appear at least once, the best way is to add all the strings right at the beginning, then add just two random Strings, and finally shuffle the list.

List<String> generatedDataList = new ArrayList<String>(indexList);
for (int i = 0; i < 2; i++)    
    generatedDataList.add(getRandomValue(indexList));
Collections.shuffle(generatedDataList);

Upvotes: 1

Zoran Regvart
Zoran Regvart

Reputation: 4690

You can shuffle the indexList by using the Collections.shuffle method, easy:

Collections.shuffle(indexList)

Upvotes: 1

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