Most frequent array of an array of arrays

Question

I made this method that takes an array of arrays and should return the array most frequent in my array of arrays, but it does print only a[0], which means that one of my expressions doesn't get evaluated. I don't understand which and why.

private static int[] frequency(int[][] a) {
    for (int z = 0; z < a.length; z++) {
        for (int t = 0; t < a[1].length; t++) {
            System.out.print(a[z][t]+" ");

        }System.out.println();}
    int count = 1, tempCount;
    int[] popular = a[0];
    int[] temp;
    for (int i = 0; i < a.length; i++) {
        temp = a[i];
        tempCount = 0;
        for (int j = 0; j < a.length; j++) {
            if ((temp == a[j])&&(i!=j)) {
                tempCount++;
            }

        }
        if (tempCount > count) {
            popular = temp;
            count = tempCount;

        }
    }

    return popular;
}

did you try a[z].length?

mac10688
– mac10688

2014-03-25 18:06:59 +00:00
Commented Mar 25, 2014 at 18:06 — mac10688
– mac10688, Commented Mar 25, 2014 at 18:06

Sergey Kalinichenko · Accepted Answer · 2014-03-25 18:07:48Z

4

You cannot compare two different arrays for element-by-element equality with this expression:

temp == a[j]

This checks reference equality only, meaning that it evaluates true only when temp is literally the same array object.

In order to fix this, replace with a call of Arrays.equals(temp, a[j])

answered Mar 25, 2014 at 18:07

Sergey Kalinichenko

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2 Comments

George Irimiciuc Over a year ago

So I should loop through each elements, instead?

Sergey Kalinichenko Over a year ago

@GeorgeIrimiciuc Essentially, yes. The need to do that is so pervasive among Java programmers, though, that Java designers have added an API to dot that (see the update to the answer).

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