You can use the Random generator to generate a random index and return the element at that index:

//initialization
Random generator = new Random();
int randomIndex = generator.nextInt(myArray.length);
return myArray[randomIndex];

You need to add logic to assign random values to double[] array using randomFill method.

Change

 public static double[] list(){
    anArray = new double[10];   
    return anArray;
 }

To

 public static double[] list() {
    anArray = new double[10];
    for(int i=0;i<anArray.length;i++)
    {
        anArray[i] = randomFill();
    }
    return anArray;
}

Then you can call methods, including list() and print() in main method to generate random double values and print the double[] array in console.

 public static void main(String args[]) {

list();
print();
 }

One result is as follows:

-2.89783865E8 
1.605018025E9 
-1.55668528E9 
-1.589135498E9 
-6.33159518E8 
-1.038278095E9 
-4.2632203E8 
1.310182951E9 
1.350639892E9 
6.7543543E7 

if you use List instead of arrays you can create simple generic method which get you random element from any list:

public static <T> T getRandom(List<T> list)
{
Random random = new Random();
return list.get(random.nextInt(list.size()));
}

if you want to stay with arrays, you can still have your generic method, but it will looks bit different

public static <T> T   getRandom(T[] list)
{
    Random random = new Random();
    return list[random.nextInt(list.length)];

}

Pseudocode:

colours <- {red, blue, green}
length <- random (0 to maxLength)
repeat length times
  colour <- pick random from colours
  append colour to outputArray
end repeat
return outputArray

Was that really so difficult?

This is one place I would definitely use streams. They have been around since Java 8 and everyone should be familiar with them. Even those new at coding in Java.

        Random r = new Random();
        int nElements = 10;
        int maxElement = 50;
        List<Integer> nums = r.ints(nElements, 1, maxElement+1).boxed().sorted()
            .collect(Collectors.toList()); 

        System.out.println(nums);

Here is the explanation.

• The first element to r.ints is the quantity. The next two are start and ending range. Since the range is exclusive, 1 must be added to include the maxElement as a possibility.
• Boxed() maps the ints to Integer objects to be collected into a List.
• Sorted() does what you would expect.
• And the collector puts them into a List

You can take input from the user by using a scanner like this -

CopyScanner input= new Scanner(System.in);
System.out.println("Enter the array size: ");
int n = input.nextInt(); 

Now create a function generateRandomArray(int n) like this -

Copypublic List<Integer> generateRandomArray(int n){
    ArrayList<Integer> list = new ArrayList<Integer>(n);
    Random random = new Random();
    
    for (int i = 0; i < n; i++)
    {
        list.add(random.nextInt(1000));
    }
   return list;
}  

Here - random.nextInt(1000) will generate a random number from the range 0 to 1000. You can fix the range as you want.

Now you can call the function with the value n get from the user -

CopyArrayList<Integer> list1 = generateRandomArray(n);
ArrayList<Integer> list2 = generateRandomArray(n);

Hope it will help.

public static Item getRandomChestItem(List<Item> items) {
    return items.get(new Random().nextInt(items.size()));
}