remove duplicate list object with condition java

Question

i have array list object, but i want to filter remove data if any duplicate id in one day.

this is my code

public static void main(String[] args) {

        ArrayList<UniqueCompletedChat> al = new ArrayList<UniqueCompletedChat>();
        al.add(new UniqueCompletedChat("2015-11-01", "D01"));
        al.add(new UniqueCompletedChat("2015-11-01", "D01"));
        al.add(new UniqueCompletedChat("2015-11-01", "D02"));
        al.add(new UniqueCompletedChat("2015-11-01", "D01"));
        al.add(new UniqueCompletedChat("2015-11-02", "D01"));
        al.add(new UniqueCompletedChat("2015-11-02", "D02"));
        al.add(new UniqueCompletedChat("2015-11-02", "D03"));
        al.add(new UniqueCompletedChat("2015-11-02", "D02"));
        al.add(new UniqueCompletedChat("2015-11-02", "D02"));
        al.add(new UniqueCompletedChat("2015-11-03", "D01"));

        List<UniqueCompletedChat> result = new ArrayList<UniqueCompletedChat>();
        Set<String> titles = new HashSet<String>();

        for (UniqueCompletedChat u : al) {
            if (titles.add(u.getIdDoctor()) || titles.add(u.getDate())) {
                result.add(u);
            }
        }

        for(UniqueCompletedChat u : result){
            System.out.print(u.getDate() + " || ");
            System.out.print(u.getIdDoctor());
            System.out.println("");
        }
}

class UniqueCompletedChat {
    private String date;
    private String idDoctor;

    public UniqueCompletedChat(String date, String idDoctor) {
        this.date = date;
        this.idDoctor = idDoctor;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public String getIdDoctor() {
        return idDoctor;
    }

    public void setIdDoctor(String idDoctor) {
        this.idDoctor = idDoctor;
    }
}

this is output from my code

my goal expectation result

how to reach my expectation? and any method elegantly to resolve this?

Minh · Accepted Answer · 2016-09-08 03:51:58Z

1

I think the bug come from this LOC:

if (titles.add(u.getIdDoctor()) || titles.add(u.getDate())) {
    result.add(u);
}

Try to combine and check it like this:

if (titles.add(u.getIdDoctor() + u.getDate())) {
    result.add(u);
}

Of course, you can use StringBuilder for better performance.

answered Sep 8, 2016 at 3:51

Minh

4244 silver badges13 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

GhostCat · Accepted Answer · 2016-09-08 03:23:05Z

1

I see two options:

Doing it by hand (looping your array and figuring duplicates)
Using a Set, and adding equals(), hashcode() methods to your class UniqueCompletedChat that simply makes two chats that have the same date and doctor ... the same chat.

Basically you have to understand your "model" that guides your design. And, if in your model such two "chats" are "the same" when they happen on the same day, with the same doctor, then your implementation should reflect that.

And, talking about good design: don't use low-level abstractions. A date, is ... a date, not a String. Probably Java has to many different ways to deal with dates, calendars, time. But well: they are there. Pick one of those. Instead of moving around Strings. Same for "DoctorID": create a class that represents that thing.

Thing is: pushing around Strings might look convenient and easy to do; but it is the opposite of a good OO design. You know, if you don't care about using Javas type system; you could as well step back and do everything in a dynamic language instead of Java.

answered Sep 8, 2016 at 3:23

GhostCat

141k28 gold badges190 silver badges262 bronze badges

1 Comment

Basil Bourque Over a year ago

Java has only two ways to deal with date-time handling: (a) the troublesome, confusing, and flawed old way (java.util.Date, java.util.Calendar, java.text.SimpleDateFormat, etc.), and (b) the modern clean powerful way in the java.time classes. Avoid any date-time class not in the java.time package.

Ramachandran.A.G · Accepted Answer · 2016-09-08 04:11:56Z

0

If you are on java 8

Collection<UniqueCompletedChat> result = al.stream()
                .<Map<String, UniqueCompletedChat>>collect(HashMap::new, (k, uc) -> k.put(uc.getKey(), uc), Map::putAll)

Just adding one method on your Chat class as :

public String getKey() {
    return this.idDoctor + this.date;
}

prints :

2015-11-02 || D02
2015-11-01 || D02
2015-11-02 || D03
2015-11-03 || D01
2015-11-02 || D01
2015-11-01 || D01

answered Sep 8, 2016 at 4:11

Ramachandran.A.G

4,9481 gold badge14 silver badges28 bronze badges

1 Comment

unknown Over a year ago

if using java 7 how to implement it?

Collectives™ on Stack Overflow

remove duplicate list object with condition java

3 Answers 3

Comments

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related