Array sort by Ascending in for loop

Question

I got trouble when i try to sort array in for loop.

I give you my code follow:

public class Lottery {

    public Lottery() {
        java.util.Random iRandom = new java.util.Random();
        int num[] = new int[6];
        java.util.Arrays.sort(num);

        for(int i =0 ; i < num.length; i++) {
            java.util.Arrays.sort(num);
            num[i] = iRandom.nextInt(49)+1;
            System.out.println(num[i]);
        }
    }

    public static void main(String[] args) {
        Lottery lott = new Lottery();
    }
}

In my above code, i can print random number for using "For Loop" but i try to sort it by ascending but it doesnt work.....

The way i do is right?

Could everybody can help me?

Thank you!

Best Regards!

you should probably generate all of the random numbers you want then call Arrays.sort(...) — Hunter McMillen
– Hunter McMillen, Commented Jul 20, 2011 at 18:25
You also need to check for duplicate random numbers. A lottery usually has unique random numbers. — Gilbert Le Blanc
– Gilbert Le Blanc, Commented Jul 20, 2011 at 18:47

Martijn Courteaux · Accepted Answer · 2011-07-20 18:37:21Z

11

Put the Arrays.sort(num) call AFTER you're finished generating the random numbers.

public Lottery(){
    java.util.Random iRandom = new java.util.Random();
    int num[] = new int[6];

    for(int i =0 ; i < num.length; i++)
        num[i] = iRandom.nextInt(49)+1;

    Arrays.sort(num);
}

edited Jul 20, 2011 at 18:37

Martijn Courteaux

69.1k48 gold badges202 silver badges297 bronze badges

answered Jul 20, 2011 at 18:26

tskuzzy

36.6k15 gold badges78 silver badges145 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

MYE Over a year ago

First of all Thank you so much I try to do follow u but when i print it , it show result such as: > 0 0 0 13 14 15 but i need range from 1-49 i dont know what problem occur Thank you !!

ryanprayogo Over a year ago

How are you printing it? There's no way to get num[i]==0 since iRandom.nextInt(49)+1 will always return an int between 1 and 49

MYE Over a year ago

It's mean can not to print from 1-49? when num[i]=0?

tskuzzy Over a year ago

Try printing the array using System.out.println(Arrays.toString(num));.

ryanprayogo · Accepted Answer · 2011-07-20 18:28:31Z

3

You're sorting the array as you go through it and inserting data into the array.

What you should be doing is:

public Lottery() {
    java.util.Random iRandom = new java.util.Random();
    int num[] = new int[6];
    //java.util.Arrays.sort(num);

    for(int i =0 ; i < num.length; i++) {
        num[i] = iRandom.nextInt(49)+1;
    }

    java.util.Arrays.sort(num);

    for(int i : num) {
        System.out.println(i);
    }
}

answered Jul 20, 2011 at 18:28

ryanprayogo

11.9k12 gold badges53 silver badges67 bronze badges

Comments

SLaks · Accepted Answer · 2011-07-20 18:25:50Z

3

You're changing the array after you sort it, which breaks the sort order.

answered Jul 20, 2011 at 18:25

SLaks

891k182 gold badges1.9k silver badges2k bronze badges

Comments

RMT · Accepted Answer · 2011-07-20 18:24:51Z

0

What you can do to sort in acceding order is:

 java.util.Arrays.sort(array);

edit: Also as said in the comments: Get the random numbers you want. Then sort in revese. (to much sorting can make the program slow)

answered Jul 20, 2011 at 18:24

RMT

7,0904 gold badges28 silver badges39 bronze badges

1 Comment

Hunter McMillen Over a year ago

he's asking about sorting in ascending order, wouldn't reverse order sort in descending?

Collectives™ on Stack Overflow

Array sort by Ascending in for loop

4 Answers 4

4 Comments

Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

4 Comments

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related