Java randomize and return an array from a function

Question

I have this function.

public static int[] createArray(){
    int[] array = new int[5];
    array = {5, 6, 8, 10, 0};
    Collections.shuffle(Arrays.asList(array));
    return array;
}

It seems I can't get the array randomized by collection directly. How can I randomize and return the array properly?

`Arrays.asList(array)` makes a copy of the array – OneCricketeer Jun 17 '18 at 19:58 — OneCricketeer, Jun 17 '18 at 19:58

score 1 · Answer 1 · answered Jun 17 '18 at 19:59

First collect the array to a List, then shuffle it and return the elements as an int[]. Something like,

public static int[] createArray() {
    int[] array = { 5, 6, 8, 10, 0 };
    List<Integer> al = IntStream.of(array).boxed().collect(Collectors.toList());
    Collections.shuffle(al);
    return al.stream().mapToInt(Integer::intValue).toArray();
}

score 1 · Answer 2 · answered Jun 17 '18 at 19:59

1

You need to store a reference to the list before you shuffle and also note that Arrays.asList(array) will yield a List<int[]> which is not what you want.

Here is one way to go about it:

 static int[] createArray(){
      int[] array = {5, 6, 8, 10, 0};
      List<Integer> temp = Arrays.stream(array).boxed().collect(Collectors.toList());
      Collections.shuffle(temp);
      return temp.stream().mapToInt(Integer::intValue).toArray();
}

answered Jun 17 '18 at 19:59

Ousmane D.

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I keep getting "The type List is not generic; it cannot be parameterized with arguments " – Nooglers BIT Jun 17 '18 at 20:09
@NooglersBIT make sure you're using `java.util.List;`. – Ousmane D. Jun 17 '18 at 20:15
yep, I do have it – Nooglers BIT Jun 17 '18 at 20:15
@NooglersBIT well, it's working on my IDE and on [**ideone**](https://ideone.com/DkHqBm) as well. – Ousmane D. Jun 17 '18 at 20:18
I am using Java compiler version 1.7. Is the problem due to this? – Nooglers BIT Jun 17 '18 at 20:23
Yup, the code in my answer is only as of JDK8. You may want to see the suggested duplicate on your post as those show solutions for JDK7. – Ousmane D. Jun 17 '18 at 20:30

Java randomize and return an array from a function

2 Answers2