My List is being sorted by the alphabetical order after sorting by date while I'm adding the 4-5 items in my List

问题

My List is being sorted by the alphabetical order after sorting by date while I am adding extra 4-5 items in my List with different names. I want to sort my List by date and time only.

here I have shared my code please help me to do so. thanks in advance.

// Filters All patient to keep only single latest record of each patient id
private List<PatientData> filterPatients(List<PatientData> allPatientData) throws ParseException {

    HashMap<String ,Pair<PatientData,Date>> filtered = new HashMap<>();
    SimpleDateFormat inSdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
    for(PatientData p : allPatientData){
        if(filtered.containsKey(p.getPatientId())){
            Pair<PatientData,Date> _p = filtered.get(p.getPatientId());
            Date d1 = _p.second;
            Date d2 = inSdf.parse(p.getScanDate());
            if(d2.after(d1)){
                filtered.put(p.getPatientId(), new Pair<>(p, d2));
            }
        }else{
            if(p.getScanDate() != null)
                filtered.put(p.getPatientId(), new Pair<>(p, inSdf.parse(p.getScanDate())));
        }
    }


    List<Pair<PatientData,Date>> filteredPairs = new ArrayList<>(filtered.values());
    Collections.sort(filteredPairs,new Comparator<Pair<PatientData, Date>>() {
        @Override
        public int compare(Pair<PatientData, Date> t1, Pair<PatientData, Date> t2) {
            if(t1.second.after(t2.second)){
                return -1;
            }else if (t1.second.before(t2.second)){
                return 1;
            }
            else
                return t1.first.getPatientId().compareTo(t2.first.getPatientId());
        }
    });
    List<PatientData> filteredList = new ArrayList<>(filteredPairs.size());



    for(Pair<PatientData,Date> p : filteredPairs){
        filteredList.add(p.first);
    }
    return filteredList;
}

回答1:

java.time

First, in your PatientData class don’t use a string for scan date. Use a date-time type and prefer the modern Instant over the old-fashioned Date. As a convenience you may have a constructor and/or a setter that accepts a string and parses it. For example:

public class PatientData {

    private String patientId;
    private Instant scanDate;

    public PatientData(String patientId, String scanDateString) {
        this.patientId = patientId;
        setScanDate(scanDateString);
    }

    public void setScanDate(String scanDateString) {
        scanDate = Instant.parse(scanDateString);
    }

    // getters, etc.
}

Now you have no need for building pairs, you can just use the PatientData class alone. To sort a list of PatientData:

    Collections.sort(filteredList, new Comparator<PatientData>() {
        @Override
        public int compare(PatientData pd1, PatientData pd2) {
            return pd1.getScanDate().compareTo(pd2.getScanDate());
        }
    });

Or if you API level is high enough (corresponding to Java 8):

    Collections.sort(filteredList, Comparator.comparing(PatientData::getScanDate));

Question: Can I use java.time on Android?

Yes, java.time works nicely on older and newer Android devices. It just requires at least Java 6.

In Java 8 and later and on newer Android devices (from API level 26) the modern API comes built-in.
In Java 6 and 7 get the ThreeTen Backport, the backport of the new classes (ThreeTen for JSR 310; see the links at the bottom).
On (older) Android use the Android edition of ThreeTen Backport. It’s called ThreeTenABP. And make sure you import the date and time classes from org.threeten.bp with subpackages.

My List is being sorted by the alphabetical order after sorting by date while I'm adding the 4-5 items in my List

问题

回答1:

java.time

Question: Can I use java.time on Android?

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