CODEWITHSUNDEEP
javaarrays
user3456
user3456

Reputation: 83

How to call Collections.Shuffle on only part of an array Java

So I have the following array:

String [] randomList = new String [16];
    randomList[0]="Dog";
    randomList[1]="Dog";
    randomList[2]="Cat";
    randomList[3]="Cat";
    randomList[4]="Mouse";
    randomList[5]="Mouse";
    randomList[6]="Car";
    randomList[7]="Car";
    randomList[8]="Phone";
    randomList[9]="Phone";
    randomList[10]="Game";
    randomList[11]="Game";
    randomList[12]="Computer";
    randomList[13]="Computer";
    randomList[14]="Toy";
    randomList[15]="Toy";

I want to shuffle only the first 9 elements of this array. I used the following code but it shuffles the entire array.

Collections.shuffle(Arrays.asList(randomList));

How would I shuffle only a part of the array rather than the whole thing? I am making quite a simple program so I would like to keep using the Collections class however all solutions are welcome. Thanks

Upvotes: 8

Views: 722

Answers (2)

Anvesh Vejandla
Anvesh Vejandla

Reputation: 221

You can also try the below. However, more cleaner code would be as suggested by templatetypedef. List<String> newList = new ArrayList<String>(); for(int i=0; i<randomList.size()-ValuePreferred; i++){ newList.add(randomList.get(i)); } Collections.shuffle(newList); randomList.removeAll(newList); newList.addAll(randomList);

Also, i hear about memory leak issue with Sublist in arrays. Not sure if that got rectified. If someone can provide any useful information regarding that would be great. Remember specifically calling value in between the List will cause IndexOutOfBoundsIssue(). That should be handled.

Upvotes: 1

templatetypedef
templatetypedef

Reputation: 372814

You can use the List type's subList method to get a List object with a view of a particular range of elements from the original list. I haven't tested this, but I think it should work:

Collections.shuffle(Arrays.asList(randomList).subList(startIndex, endIndex));

Upvotes: 11

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