Trying to understand how these two types of code work?

**archangl1** · February 8th, 2022, 01:27 AM

Well a little background I am starting to get back into coding, so the language I am using is Java. I cam across this website called Hacker Rank, which give different problems to solve. One of them is dealing with Lists, which I have never encountered until now. So I started looking at different places to try and how to solve the problem. I ran into this piece of code:

  // Overriding compare()method of Comparator 
                        // for descending order of cgpa
            public int compare(Student s1, Student s2) {
                if (s1.cgpa < s2.cgpa)
                    return 1;
                else if (s1.cgpa > s2.cgpa)
                    return -1;
                                return 0;
                }

I am trying to in the else if statement two integers are sent. I am trying to understand why send -1 and then 0, instead just 0 by itself. I just figured that by sending the lower integers is to make sure that it is sorted appropriately (correct me if I am wrong on my thinking).

The second issue I am having is the comparing using subtracting. I am trying to understand how that work?

**Norm** · February 8th, 2022, 06:59 AM

Look at the API doc for the compare method of the Comparator interface. It explains what values the method should return.

Please edit your post and wrap your code with code tags:

[code]
**YOUR CODE GOES HERE**
[/code]

to get highlighting and preserve formatting.

**archangl1** · February 8th, 2022, 12:13 PM

Originally Posted by Norm

Look at the API doc for the compare method of the Comparator interface. It explains what values the method should return.

Please edit your post and wrap your code with code tags:

[code]
**YOUR CODE GOES HERE**
[/code]

to get highlighting and preserve formatting.

Ok no prob. Thanks.

**LeslieS** · February 10th, 2022, 11:21 PM

This is a case of the code not being formatted very well. The last line 'return 0;' is not inside the if/else blocks.
Because the if and the else are not using {}, they are single line statements.
If the first condition is true 1 is returned.
If the second condition is true -1 is returned.
Otherwise 0 is returned.
Here is what it looks like if it is aligned more clearly.

// Overriding compare()method of Comparator 
// for descending order of cgpa
public int compare(Student s1, Student s2) {
    if (s1.cgpa < s2.cgpa) return 1;
    else if (s1.cgpa > s2.cgpa) return -1;
    return 0;
}

or with {} to better show it:

public int compare(Student s1, Student s2) {
    if (s1.cgpa < s2.cgpa) {
        return 1;
    }else if (s1.cgpa > s2.cgpa) {
        return -1;
    }
    return 0;    // this is returned when the items are equal
}

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