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up vote 0 down vote favorite

I implemented my own class myclass. I wrote following code for sorting

Arrays.sort(arrayForSortingInterval, new Comparator<myclass>() {
    public int compare(myclass o1, myclass o2) {
        return o1.minute <= o2.minute ? 1 : 0;
    }
});

My array is declared as myclass[] arrayForSortingInterval = new myclass[lengthIntervalArray*2]; and myclass has two integer values minute and tag.

But this sorting code doesn't seem to work.

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5  
What does doesn't seems to work mean? What do you expect, what do you get? – Sotirios Delimanolis Jan 14 '14 at 15:45
    
Please use Java naming conventions, classes should be in UpperCamelCase. – Boris the Spider Jan 14 '14 at 15:46
2  
Your compare method never returns -1. Why don't you use Integer.compare(o1.minute, o2.minute); ? – user2336315 Jan 14 '14 at 15:47

4 Answers 4

up vote 4 down vote accepted

The compare method needs to return a negative number when the left object is less than the right one, zero when the two are equal, and a positive number when the left object is greater than the one on the right. One way of achieving this is calling Integer.compare (assuming that minute is an int in your myclass class):

public int compare(myclass o1, myclass o2) {
    return Integer.compare(o1.minute, o2.minute);
}
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up vote 3 down vote

Your comparator is wrong. It should: Returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.

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up vote 1 down vote

You comparator method is incorrect, since it is not antisymmetric (compare a to b returns 1, then b to a returns 0).

you should simply return o1.minute - o2.minute

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up vote 0 down vote

Your compare function is incorrect -1, 0 or 1 for less then, equals or greater respectively.

public int compare(myclass o1, myclass o2) {
  // return o1.minute <= o2.minute ? 1 : 0;
  if (o1.minute < o2.minute) {
    return -1;
  } else if (o1.minute > o2.minute) {
    return 1;
  }
  return Integer.compare(o1.tag, o2.tag);
}
share|improve this answer
    
That's complicated. – Moritz Petersen Jan 14 '14 at 15:50
    
@MoritzPetersen I assume OP wants to compare tag as well, otherwise why mention the field? Perhaps I over-thought it. – Elliott Frisch Jan 14 '14 at 15:53

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