Sort random array in ascending order without arrays.sort

Question

I am trying to sort an array of random numbers without using the arrays.sort. I have the code, but it doesn't work. not sure where is the error. Any kind of help is appreciated.

import java.util.*;
public class Sort
{
    public static void main(String args[])
    {
        Scanner in = new Scanner(System.in);
        System.out.print("How many numbers do you want? ");
        int howMany = in.nextInt();
        int [] myArray =  getRandomArray(howMany);

    }

    /* public static int bsearch(int[] arr, int key)
    {

    }*/

    public static int[] getRandomArray(int howMany) {
        int[] returnMe = new int[howMany]; // Assume size >= 0
        Random rand = new Random();
        for (int i = 0; i < howMany ; i++) 
        returnMe[i] = rand.nextInt(Integer.MAX_VALUE) + 1;
        //System.out.print(returnMe[i] + " ");
        for (int i = 1; i <= (howMany - 1); i++)
        {
            for (int j = 0; j < howMany - i -1; j++) 
            {
                int tmp = 0;
                if (returnMe[j] > returnMe[j+1])
                {
                    tmp = returnMe[j];
                    returnMe[j] = returnMe[j + 1];
                    returnMe[j + 1] = tmp; 
                }   
            }  
        }
        for ( int i = 0; i < howMany; i++)
            System.out.println(returnMe[i] + " "); 
        return returnMe;
    }
}

"Does not work" means what, exactly? Does not compile? Compiles, but does not run? Compiles and runs be emits an error (which?) or other incorrect output? — John Bollinger
– John Bollinger, Commented Apr 18, 2017 at 20:45
It compiles, run and gives output, but not in an ascending order(just random order) @JohnBollinger — rancer
– rancer, Commented Apr 18, 2017 at 20:47
You do realize, do you not, that you need to do more than name your class "Sort" to get it to perform actual sorting? Because I don't see anything whatever in it that would do any sorting. — John Bollinger
– John Bollinger, Commented Apr 18, 2017 at 20:47
@DiabolicWords I am using BlueJ and it is not sorting it in ascending order. — rancer
– rancer, Commented Apr 18, 2017 at 20:48
@JohnBollinger I have the coding in the getRandomArray method, it is the bubble sort method. You say , that it is wrong? — rancer
– rancer, Commented Apr 18, 2017 at 20:50

ptstone · Accepted Answer · 2017-04-18 20:55:16Z

1

Your line

        for (int j = 0; j < howMany - i -1; j++)

should be

        for (int j = 0; j <= howMany - i -1; j++)

or alternatively, remove the "-1" and keep "<". Otherwise, you will ignore the last number in the array. Everything else looks fine to me.

answered Apr 18, 2017 at 20:55

ptstone

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1 Comment

ptstone Over a year ago

Happy to help :). Also, you could consider renaming the method to something like createRandomSortedArray, since createRandomArray implies its a yet-to-be sorted array. However, thats just to make the code easier to read&understand for others (which can actually be quite important if you don't just code for yourself).

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