Compare values of Pairs and sort them

Question

I have Pairs that I would like to sort. I have already done the compare implementation and it seems to be working.

I also saw a solution online but the problem is that it doesn't allow it to be static.

public static ArrayList <Pair<Integer, Integer>> pairList = new ArrayList<Pair<Integer, Integer>>();    

public static Pair<Integer, Integer> pair1 = new Pair<>(6, 7);
public static Pair<Integer, Integer> pair2 = new Pair<>(7, 7)

This is where I'm getting the Error Change compare() to static with the solution that I'm testing out.

Method that I'm testing out:

public  class MachineNoComparator implements Comparator <Pair<Integer, Integer>> {
    public int compare(Pair<Integer, Integer> o1, Pair<Integer, Integer> o2) {
        return o1.getMachineNo().compareTo(o2.getMachineNo());
    }
}

It sounds like you don't really understand what the static keyword does. That should be your first step. — Kevin Workman, Apr 22 '15 at 14:20
Some code seems to be missing. Where do you get "the error"? — Seelenvirtuose, Apr 22 '15 at 14:24
@Gana, I am not sure I have understood the issue: you mean it won't work if I change the compare method to make it static? — alainlompo, Apr 22 '15 at 14:24
No worries guys I have fixed it. The problem was solved by removing implements Comparator from the class. — Gana, Apr 22 '15 at 14:28

score -1 · Answer 1 · answered Apr 22 '15 at 14:34

You probably call compare as

compare(pair1,pair2);

pair1 and pair2 are static and compare not. When you pass static fields to a function, the function also has to be static. This is the reason of why you take this error.

You can solve this by changing compare method to;

public static int compare(Pair<Integer, Integer> o1, Pair<Integer, Integer> o2) {
    return o1.getMachineNo().compareTo(o2.getMachineNo());
}

or fields to;

public Pair<Integer, Integer> pair1 = new Pair<>(6, 7);
public Pair<Integer, Integer> pair2 = new Pair<>(7, 7);

But you should have a look what 'static' keyword is and what it does.

Compare values of Pairs and sort them

1 Answers1