Compare two Java Collections using Comparator instead of equals()

Question

Problem Statement

I have two Collections of the same type of object that I want to compare. In this case, I want to compare them based on an attribute that does not fa

Answer 1

I'm not sure this way is actually better, but it is "another way"...

Take your original two collections, and create new ones containing an Adapter for each base object. The Adapter should have .equals() and .hashCode() implemented as being based on Name.calculateWeightedRank(). Then you can use normal Collection equality to compare the collections of Adapters.

* Edit *

Using Eclipse's standard hashCode/equals generation for the Adapter. Your code would just call adaptCollection on each of your base collections, then List.equals() the two results.

public class Adapter {

    public List adaptCollection(List names) {
        List adapters = new ArrayList(names.size());

        for (Name name : names) {
            adapters.add(new Adapter(name));
        }

        return adapters;
    }


    private final int name;

    public Adapter(Name name) {
        this.name = name.getWeightedResult();
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + name;
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Adapter other = (Adapter) obj;
        if (name != other.name)
            return false;
        return true;
    }

}