Creating HashSet from float[][] array

Question

I just started learning Java and barely know about primitive class and a data type, and I was trying to create a set for every array inside another array. But when I tried doing it the result wasn't a set of the contents of the inner array, but a set of the array itself.

In Python I would just do:

mylist = [[1, 1, 1], [0, 0, 0], [0, 0, 0]]
for inner in mylist:
    s = set(inner)

And s would just be 1, 0, 0 (for each loop).

But when I tried implementing this in Java I got a size of 1 (which would be correct for my example) but when I displayed the set's items it's a random set of letters and numbers (I saw in another post that this is a memory address). I was just hoping anyone would point out where my mistake is and how to implement it correctly.

Code:

public class Test {
    private static final int HOURS = 24;
    private static final int DAYS = 3600;
    private static float[][] mylist = new float[DAYS][HOURS];
    
    private static void set_loop(float[][] myList) {
        for (int k = 0; k < myList.length; k++) {
            Set<float[]> mySet = new HashSet<>(Arrays.asList(myList[k]));
            System.out.println("------------------");
            System.out.println(mySet.size());
            for (float[] s : mySet) {
                System.out.println(s);
            }           
        }
    }
    
    public static void main(String[] args) {
        for (int k = 0; k < mylist.length; k++) {
            for (int i = 0; i < mylist[k].length; i++) {
                if (k == DAYS - 2) {
                    mylist[k][i] = 9;
                } else {
                    mylist[k][i] = 0;
                }
            }           
        }
        set_loop(mylist);
    }
}

Don't mix arrays and generics together. Instead of Set<float[]> use Set<List<Float>>. — Alexander Ivanchenko
– Alexander Ivanchenko, Commented Feb 21, 2022 at 13:25
result wasn't a set of the contents of the inner array - so your desired result is just a set of numbers and not a set of arrays? — Alexander Ivanchenko
– Alexander Ivanchenko, Commented Feb 21, 2022 at 13:27
@AlexanderIvanchenko, I wanted a set of the floats inside of the array, but when I print what's in the set, I get the same array I wanted to make a set of. — DheltaHalo
– DheltaHalo, Commented Feb 21, 2022 at 14:31
Then Arrays utility class will give you a hand with it. Use Arrays.toString(arr) for that purpose. — Alexander Ivanchenko
– Alexander Ivanchenko, Commented Feb 21, 2022 at 14:38

Peter Moss · Accepted Answer · 2022-02-21 12:55:39Z

1

In case your output looks something like this: 52e922, then you probably just need to do System.out.println(Arrays.toString(s)); in order to print the array correctly.

answered Feb 21, 2022 at 12:55

Peter Moss

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