Creating a Random Array Method

Question

I have the following code:

import java.util.*;

public class Lab7 {

/**
 * @param args
 */

public static void main(String[] args) {
    // TODO Auto-generated method stub

    double[][] g = { { 0, 1, 2 }, { 1, 0, 3 }, { 2, 3, 0 } };
    double mst[][] = MST.PrimsMST(g);
    PrintArray(g);                                                                      
    PrintMST(mst);
}

public static void PrintArray(double[][] g) {

    System.out.println(Arrays.deepToString(g));

}

public static void PrintMST(double[][] mst) {

    System.out.println(Arrays.deepToString(mst));

}

}

I really need help in adding a RandomArray method that will create a random array for me (g) as opposed to me having to enter the values of the multidimensional array myself.

Here's a piece of code I used before to create a random array:

I can't seem to modify it however to use in the above code, can anyone help me please?

public static ArrayList<Integer> RandomArray(int n)   {                 // Method called RandomArray which takes a     parameter as an integer  
    ArrayList<Integer> randomArray = new ArrayList<Integer>(n);         // Creates an ArrayList called randomArray, of size 'n'
    Random randNumGenerator = new Random();                             // Creates a random object
    for (int i = 0; i < n; i++){                                        // Creates a for loop which goes from i=0 to 'n'
        randomArray.add(new Integer(randNumGenerator.nextInt(256)));    // Will add a random int from 0 to 255, in the array 'randomArray'
    }
    return randomArray;                                                 // Returns randomArray
}

Actually you can't use it in your original code. Because you generated an ArrayList, whereas you need an array of array. — Rohit Jain
– Rohit Jain, Commented Nov 22, 2012 at 18:40
You could do ArrayList<ArrayList<Integer> > which uses the old RandomArray for each row. — Barney Szabolcs
– Barney Szabolcs, Commented Nov 22, 2012 at 18:41
This question is probably asked, in one form or another, about twice a week. If the version you're cribbing from doesn't work for you, find another one. — Hot Licks
– Hot Licks, Commented Nov 22, 2012 at 18:44

jlordo · Accepted Answer · 2012-11-22 18:44:10Z

1

Changed your method to fit your needs:

public static double[] randomArray(int n) {
    double[] randomArray = new double[n];
    Random randNumGenerator = new Random();
    for (int i = 0; i < n; i++) {
        randomArray[i] = randNumGenerator.nextDouble() * 256;
    }
    return randomArray;
}

now you could call it like

double[][] g = {randomArray(3), randomArray(3), randomArray(3)};

answered Nov 22, 2012 at 18:44

jlordo

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1 Comment

Makoto Over a year ago

It doesn't have to be double; you could cast them to int as well.

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