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 

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.

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];

To generate a random integer, you're best off using this:

Random rand = new Random();
numbers[i] = rand.nextInt(20)+1;

The rand.nextInt(20) call will give a random number from 0 to 19, so adding 1 makes it from 1 to 20.

In practice, you don't need to create a new Random() every time; you'd put this

Random rand = new Random();

at the beginning of your loop, and then

numbers[i] = rand.nextInt(20)+1;

inside it.

Since you've got several errors, I'd suggest you start again, write your code bit by bit, and check at each stage that it compiles and does what you want. For instance, start by printing a single random number out, and check that that works.

It should be like

 ar1[i] = (int)(Math.random() * 100);

When you cast, cast type should be in brackets e.g. (cast type)value

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

The main thought of what you want to do is to get all the numbers inside an array and then suffle them.

Firstly, you must create an array with all the numbers that you want. In your case the numbers that you want are from 0 to NumberOfPairs two times. For example if the NumberOfPairs = 3, then the numbers that you have are (0, 0, 1, 1, 2, 2). Therefore, you got this code:

import java.util.Random;

public class Board {
    private int NumberOfCards;
    private int NumberOfPairs;
    private int[] DeckOfCards;
    private int CardsRemaining;
    
    public Board(int NumberOfPairs){
        this.NumberOfPairs = NumberOfPairs;
        this.NumberOfCards = NumberOfCards*2;
        this.CardsRemaining = CardsRemaining;
        DeckOfCards = new int [2*NumberOfPairs];
        Random numbers = new Random();

        for (int i = 0; i < NumberOfCards; i++) {
            for (int j = 0; j < 1; j++) {
                DeckOfCards[i] = i;
            }
        }
    }
}

And finally, you must suffle the numbers. To suffle the numbers, you have to switch every current position of the array with a random one. So, for this step your code is something like this:

import java.util.Random;

public class Board {
    private int NumberOfCards;
    private int NumberOfPairs;
    private int[] DeckOfCards;
    private int CardsRemaining;
    
    public Board(int NumberOfPairs){
        this.NumberOfPairs = NumberOfPairs;
        this.NumberOfCards = NumberOfPairs*2;
        this.CardsRemaining = CardsRemaining;
        DeckOfCards = new int [2*NumberOfPairs];
        private int temp;
        private int randomPos;

        Random numbers = new Random();
        for (int i = 0; i < NumberOfCards; i++) {
            for (int j = 0; j < 1; j++) {
                DeckOfCards[i] = i;
            }
        }
        
        for (int i = 0; i < NumberOfCards; i++) {
            randomPos = random.nextInt(NumberOfCards);
            temp = DeckOfCards[i];
            DeckOfCards[i] = DeckOfCards[randomPos];
            DeckOfCards[randomPos] = DeckOfCards[temp];                
        }
    }
}

And you are done. I hope that I helped you.