Java - Set<ObjectA> removeAll(Set<ObjectB>) does not do its job

Question

I have got a Set A, and a Set B. What I want to do is Set A - set B by using Set A.removeAll(Set B).

I have already overrided both equals() and hashCode() function as follows:

GooleGeometryPoint.class

@Override
public int hashCode() {
    return new HashCodeBuilder(17, 31) // two randomly chosen prime numbers
                    .append(postalcode)
                    .toHashCode();
}

@Override
public boolean equals(Object obj) {

    if (!(obj instanceof GoogleGeometryPoint))
        return false;
    if (obj == this)
        return true;

    if(postalcode.equals(((GoogleGeometryPoint) obj).getPostalcode())) {
        return true;
    }
    return false;
}

Main.class

Set<GoogleGeometryPoint> onlinePostalcodes;
Set<GoogleGeometryPoint> offlinePostalcodes;

//Get all complaints
        complaints =
                CsvParser.parseCsv(Constants.FILE_KLACHTEN_CSV)
                        .stream()
                        .map(k -> CsvParser.mapToKlachtModel(k.toString()))
                        .collect(Collectors.toList());

        //Get all offline postalcodes with coordinates
        offlinePostalcodes =
                CsvParser.parseCsv(Constants.FILE_POSTAL_CSV)
                        .stream()
                        .map(p -> CsvParser.mapToGoogleGeometryPoint(p.toString()))
                        .collect(Collectors.toSet());


        //Copy complaints into set
        onlinePostalcodes = complaints
                .stream()
                .map(e -> new GoogleGeometryPoint(e.getPostalcode(), e.getStreet(), e.getCity()))
                .collect(Collectors.toSet());


        //Remove all the postalcodes that are already offline available
        onlinePostalcodes
                .stream()
                .filter(e -> e.getPostalcode() != null)
                .collect(Collectors.toSet())
                .removeAll(offlinePostalcodes);

After calling the removeAll() method, onlinePostalcodes seems to contain the same objects as before, nothing is removed. Is there anything wrong with my logic? Any help would be highly appreciated.

Answer 1

By using .collect(Collectors.toSet()) you create a new object from which you delete. You do not change onlinePostalcodes. Maybe you intended to write

    onlinePostalcodes = onlinePostalcodes
            .stream()
            .filter(e -> e.getPostalcode() != null)
            .collect(Collectors.toSet());

    onlinePostalcodes.removeAll(offlinePostalcodes);