Question

I am creating random number generator in Java as part of program I am writing to learn the language better (come from more C#/C++ background).

    ArrayList<Integer> al = new ArrayList<Integer>();
    Random ran = new Random();
    for(int i = 1; i <= 11; i++)
        al.add(i);


    for(int i = 0; i < 2; i++)
    {
        ArrayList<Integer> temp = new ArrayList<Integer>();
        int num = al.remove(ran.nextInt(al.size()));

        temp.add(num);
        Arrays.sort(temp);

        text("\Random Number " + i + " is: " + temp[i]);
    }

On arrays.sort(temp) I get a no suitable method error and in my text output function I get array required but java.util.ArrayList found. Can anyone suggest a better way to sort this random number array into ascending order or see something I am doing wrong currently that could easily be corrected? Thanks.

Answer 1

Use Collections.sort(temp).

In Java, arrays and lists are two different beasts. Arrays.sort() only works for arrays; the equivalent function for lists is Collections.sort().

I can’t say I fully understand the logic behind your code, but you might also want to take a look at Collections.shuffle().

edit Upon closer inspection, there are other problems with the code:

1. You are re-creating temp from scratch, so on each loop iteration it will contain exactly one element.
2. temp[i] is not valid syntactically; the correct syntax is temp.get(i). Even with the correct syntax, it’ll give you an “out of bounds” exception, since temp only contains one element.