I'm creating a very simple form validation utility for a sign up screen, and I'm running into some unexpected behavior concerning LinkedHashMap and a stream created from its entrySet.

I'm storing validation results in a LinkedHashMap, with the following ordering of statements:

Map<ValidationResult.SignUpField, Boolean> fieldStatuses = new LinkedHashMap<>();

fieldStatuses.put(EMAIL, isValidEmail(emailAddress));
fieldStatuses.put(USERNAME, isValidUsername(username));
fieldStatuses.put(BIRTHDAY, isValidBirthday(birthday));
fieldStatuses.put(PASSWORD, isValidPassword(password));
fieldStatuses.put(CONFIRM_PASSWORD, password.equals(confirmedPassword));

List<ValidationEntry> invalidFields = aggregateInvalidFields(fieldStatuses);

One particular iteration yields all of the above fields invalid except for "confirm password". Using a simple for loop over the entry set and omitting valid results, the invalid results appear in the following order:

• Email
• Username
• Birthday
• Password

I then attempted to make use of the subset of Stream API's available on Android (targeting version 25 with a min of 19, hence the lack of Collectors.toMap()):

private static List<ValidationEntry> aggregateInvalidFields(Map<ValidationResult.SignUpField, Boolean> fields) {
    List<ValidationEntry> invalidFields = new ArrayList<>();
    fields.entrySet()
            .stream()
            .filter(entry -> !entry.getValue())
            .forEachOrdered(entry -> {
                ValidationResult.SignUpField field = entry.getKey();
                invalidFields.add(new ValidationEntry(field, lookUpErrorCode(field)));
            });
    return invalidFields;
}

But that code yields the following order:

• Birthday
• Password
• Username
• Email

What exactly is happening here, why is the result of the stream not honoring the insertion order of the LinkedHashMap? Note that if I swap out forEachOrdered with forEach, it's still not insertion ordered.