sort a List based on a parameter available in another class

Question

I have some design problems with Java Comparator Interface.

I have a class which contains a Set of a simple custom data structure:

Answer 1

I assume that you have a List stored somewhere.. In Comparator, you need to invoke a getDataById method from your data class, and sort through Priority..

Check the below code.. I have used a single class for many purpose..

Ideally you would want to break it into more classes.. But this is just a Demo, how to achieve what you want..

class Container {
    // List of Data  instances created..
    // This list has to be static, as it is for a class, 
    // and not `instance specific`
    public static List dataList = new ArrayList();

    // List of Ids, that you want to sort.
    private List idList = new ArrayList();

    // Populate both the list..

    // Have a method that will iterate through static list to 
    // find Data instance for a particular id

    public static Data getDataById(long id) {
        // Find Data with id from the list

        // Return Data
    }

    public void sortList() {
        Collections.sort(idList, new MyComparator());
    }
}

public MyComparator implements Comparator {

    public int compare(Long int1, Long int2) {
        Data data1 = Container.getDataById(int1);
        Data data2 = Container.getDataById(int2);

        return data1.getPriority() - data2.getPriority();
    }
}