Sort integer array based on custom comparator

Question

This is something simple but I'm obviously missing something....

I have a 2D array that contains integer representations of Color values that have been calculated from a BufferedImage object. I also have a method to calculate the brightness value based on the integer values.

I want to sort rows based on the brightness value. However, I'm getting

sort(java.lang.Integer[], Comparator<? super Integer>) in Arrays cannot be applied
to (int[], IntComparator)

My comparator method:

private class IntComparator implements Comparator<Integer>{
  @Override
  public int compare(Integer x, Integer y){
    return (PhotoUtils.getBrightnessValue(x) <= PhotoUtils.getBrightnessValue(y)) ? x : y;
  }
}

Inside my sortRow method, I have

public void sortRow(int row) {
  Arrays.sort(this.buffer[row], new IntComparator());
}

What is the issue here? After all, I'm just calculating two integer values based on the input and returning either < 0 or > 0.

You're conflating int[] and Integer[]. Note that you can autobox/auto-unbox from int to Integer and vice versa, but not from Integer[] to int[] and neither vice versa. — Taylor
– Taylor, Commented Dec 11, 2013 at 2:41

Óscar López · Accepted Answer · 2013-12-11 02:54:12Z

3

Make sure to declare the buffer attribute as an Integer[], because you defined the comparator for the Integer type, not for the int type - and the sort() method that receives a Comparator will only work for arrays of object types, not for arrays of primitive types such as int.

Be aware that an int[] can not be automatically converted to Integer[], it might be necessary to explicitly create a new Integer[] and copy the int[] elements into it:

int[] myIntArray = ...;
Integer[] myIntegerArray = new Integer[myIntArray.length];
for (int i = 0; i < myIntArray.length; i++)
    myIntegerArray[i] = myIntArray[i]; // autoboxing takes care of conversion

edited Dec 11, 2013 at 2:54

answered Dec 11, 2013 at 2:46

Óscar López

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Sotirios Delimanolis · Accepted Answer · 2013-12-11 02:46:12Z

1

The Arrays.sort(T[], Comparator) is a generic method where both the first and second parameters use the type variable. Since primitives can't be used as generic type arguments, ex. Comparator<int>, you cannot pass an int[] as the first argument.

You will need to pass an Integer[].

answered Dec 11, 2013 at 2:46

Sotirios Delimanolis

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