TreeSet is an ordered data structure, thus each insert has time complexity O(log(n)). How do I efficiently iterate over each entry in a Java Map? (Student supplier is a simple supplier function of list of students), Note: Only duplicate records with studentName matching and percentage 100 must be removed,(Record Ronon has percentage 100 but there is no duplicate with the same studentname so that must not be removed). This assumption is based on pure logic: such element can not be considered as a duplicate because it's name attribute is unique. doubly-linked list running through all of its entries. java - How to remove duplicate objects in a List<MyObject> without Thanks for the solution,indeed it worked and sorry for late reply. It's one of a few different plausible takes on the requirement, which doesn't fully cover all edge cases. and what if, Don't know why someone gave down vote, this answer gives the desired output, haven't voted, but there is no duplicate name for, what if ronan has 100 percentageit shouldn't be removed since it is not a duplicateas there is only one entry with name ronan, @Holger The collection is required as you cannot process a stream twice; I need to "tee" the stream into two results. Do the subject and object have to agree in number? If you want to maintain the order of the items in the original list, instantiate LinkedHashSet instead of HashSet. This linked He might've included other fields? When we create a LinkedHashSet instance using the List, it removes all the duplicates from the List and maintains the order of the elements. How to Remove Duplicate Elements from a Java List - amitph Let's say the rule is simply: Delete all students with attendence = 100, but only if there is a record with the same name with an attendence below 100. The process of populating each deque (which basically is used as a Stack data structure) will be governed with the provided predicate. Term meaning multiple different layers across many eras? There's source and destination. The primary issue is that your data storage mechanism is not in an appropriate form for this job. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. Please note that we can use HashSet to remove duplicate elements from a List, but it is an unordered collection and will not honour the order of the elements in . Can someone help me understand the intuition behind the query, key and value matrices in the transformer architecture? Is Java "pass-by-reference" or "pass-by-value"? Geonodes: which is faster, Set Position or Transform node? Java Set is a distinct collection of elements. If a crystal has alternating layers of different atoms, will it display different properties depending on which layer is exposed? Java 8 Stream remove "almost" duplicates from list? Is there a word for when someone stops being talented? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing. The final snippet had a bug in it; I fixed it now. I need to remove duplicate objects from a list based on some properties and have distinct values. 592), Stack Overflow at WeAreDevelopers World Congress in Berlin, Temporary policy: Generative AI (e.g., ChatGPT) is banned. Making statements based on opinion; back them up with references or personal experience. Can I spin 3753 Cruithne and keep it spinning? I need to remove the objects having same id and value and having status 'COMPLETE'. How difficult was it to spoof the sender of a telegram in 1890-1920's in USA? How can kaiju exist in nature and not significantly alter civilization? How to avoid conflict of interest when dating another employee in a matrix management company? How did this hand from the 2008 WSOP eliminate Scott Montgomery? Does this definition of an epimorphism work? How do I read / convert an InputStream into a String in Java? By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. Notice that any combination of two character is same, e.g: 'a' + 'b' = 195 = 'b' + 'a', so first time we see a combination 'a' + 'b' we set that index-195 to '1' and second time when we see that 'b' + 'a' and see that index-195 is already 1, then we can safely say that its a repetition. How to remove Duplicated elements from a List based on Two properties using Java 8 streams? Do Linux file security settings work on SMB? Thanks for contributing an answer to Stack Overflow! More generally using streams here is complicated. Why do capacitors have less energy density than batteries? How to use smartctl with one raid controller, Is this mold/mildew? @vinS: No, i mean (a,b) and (b,a) are duplicates. How to remove duplicate in List<T> JAVA 8 - Stack Overflow Remove Duplicates From a List Using Plain Java and I have no idea how to put an another condition here to keep the one with the largest age. c# list remove item based on property duplicate; remove duplicated from array of ojects; kotlin remove duplicates from list; java remove duplicates; does set automatically get rid of duplicates in java; Program to remove duplicates in an ArrayList; java remove duplicates; asscending linkedlist remove duplicates valuesjava; django model remove . What happens if you have 2 records with name =. Thanks, actually i am looking for some solution using java 8 features rather than Override equals and hashcode. Not the answer you're looking for? Removing duplicates from the list of objects based on more than one When to use LinkedList over ArrayList in Java? A stream-based implementation may look like this: If we do not like the stream-based approach, we can also solve this with a "traditional", imperative approach: The deduplication does not come "for free". If I understood your goal correctly, you want to remove only elements having a value of null if there's at least one more element that has the same name. How do I declare and initialize an array in Java? Not the answer you're looking for? An auxiliary map generated by this collector will what the following structure Map>. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing. Java 8 Distinct by property, Remove duplicates from a list of objects based on property in Java 8. Question based on https://stackoverflow.com/a/29671501/2517622. In order to achieve this, I've written a custom collector that can be vaguely compared with Collectors.groupingBy. How feasible is a manned flight to Apophis in 2029 using Artemis or Starship? without looping through 100 million entries which is a non-trivial job. - Madbreaks Sep 27, 2017 at 21:50 great answer howtodoinjava.com/java8/java-stream-distinct-examples - Dusman Feb 23, 2020 at 11:45 Add a comment 9 Answers Sorted by: 190 Connect and share knowledge within a single location that is structured and easy to search. 592), Stack Overflow at WeAreDevelopers World Congress in Berlin, Temporary policy: Generative AI (e.g., ChatGPT) is banned. Connect and share knowledge within a single location that is structured and easy to search. desire output After removing the duplicates: What i have right now is only removing duplicates based on the name and not considering the percentage(100)and also not preserving the order..any help is greatly appreciated. rev2023.7.24.43543. How can kaiju exist in nature and not significantly alter civilization? What are some compounds that do fluorescence but not phosphorescence, phosphorescence but not fluorescence, and do both? Connect and share knowledge within a single location that is structured and easy to search. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. It should cast to the same class where this method is defined: DataClass. In order to make the method responsible for creation of the collector to be uniform and reusable, it utilizes generics and expects two parameters mentioned above: a function and a predicate. Find centralized, trusted content and collaborate around the technologies you use most. like below link they have solution on one property. I am trying to remove duplicates from the list of objects based on two properties, this question would be similar to below link but I am trying to find uniqueness based on two properties using java 8 features. Then iterate over the list and insert each element to the map using: mymap.put(source.year, source); Then remove all elements from the origianl list and iterate over the map and insert each element to the list. Do US citizens need a reason to enter the US? Why does ksh93 not support %T format specifier of its built-in printf in AIX? "Fleischessende" in German news - Meat-eating people? Do Linux file security settings work on SMB? you can add values in a Map (where string is name) only if age is greater of equals than the one in the map. Removing duplicates from the list of objects based on more than one property in java 8. Not the answer you're looking for? Here's a much simpler algorithm: This assumes that the implementation of the equals method is fixed. 1 From extensibility point of view I'm wondering if the asker really wants to have equals & hashCode or maybe it would be enough to have a custom comparator and a collection backed by it. Hot Network . 592), Stack Overflow at WeAreDevelopers World Congress in Berlin, Temporary policy: Generative AI (e.g., ChatGPT) is banned. If id and name are equal the "status" element will be checked. Thanks for contributing an answer to Stack Overflow! @RobertMoskal: the question is, rather, why you'd want to sneak around implementing. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. The other variant does the same, but doesn't use streams: ernest_k answer is great but if you maybe want to avoid adding duplicates you can use this: Just use addToEmployees method to add Employee to your list. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Thank you Eritrean..your solution has covered my scenarios..thankyou very much.i don't have enough votes to up your solution.thankyou very much, how is the output distinct based on keys? Can somebody be charged for having another person physically assault someone for them? Below given is a function that accepts varargs parameters and returns a Predicate instance. @burquete Actually, OP did specify in his comment under the question: "I've already overridden the hashcode and equals method", yes but you can overrode & include a logic that wouldn't make those 4 variables as the unique hash values, right? like this lambda for the key mapper: How does this work? How can the language or tooling notify the user of infinite loops? Using robocopy on windows led to infinite subfolder duplication via a stray shortcut file. How can I avoid this? How do I enhance this Duplicate objects from List method using Java 8? Any subtle differences in "you don't let great guys get away" vs "go away"? I need to filter based on three conditions: same id, value and status = 'COMPLETE'. If these properties are never null, you could use Java9s List.of instead of Arrays.asList which is potentially more efficient. Remove Objects with a duplicate ID from a list? why didn't you just add a .filter(e -> ) on your Stream? How to use smartctl with one raid controller, My bechamel takes over an hour to thicken, what am I doing wrong. Apart from the accepted answer, here are two variants: This one uses Collectors.toMap to group employees by name, letting Employee instances as the values. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing. Alternatively, we can use one of the Java Set implementations to deduplicate a Java List. (O(n), to be algorithmically specific: Making a set-based duplicate requires constant-time steps per student record, so O(n), and the removeIf call similarly requires checking each student, but only having to do constant-time work per step, because .contains() on a set is constant time assuming good hash distribution, which Strings usually have), thus, a constant amount of O(n) operations means the whole operation is O(n): The time it takes grows linearly with how many students are in your input list (vs solutions that involve scanning the whole list every time you process a single entry in the list, which grows with the square of the input size). Connect and share knowledge within a single location that is structured and easy to search. So here is my updated ObjectClass instead of DataClass including correct overridden equals method, 2) After fixing equals method I tried below implementation in removeDuplicate method as Janos mentioned and it is working fine as expected. How many alchemical items can I create per day with Alchemist Dedication? How do I generate random integers within a specific range in Java? Some of them are. Given a list of employees with id, name and IQ: So, remove duplicates from the list based on id property of employee and choose employee with the highest IQ for obvious reasons. To learn more, see our tips on writing great answers. English abbreviation : they're or they're not. I don't want to filter out complete status. Not the answer you're looking for? The equals method compares i and j variables, Just a simple suggestion for improving performance. How can the language or tooling notify the user of infinite loops? Mar 10, 2018 at 19:28. Do US citizens need a reason to enter the US? Connect and share knowledge within a single location that is structured and easy to search. Create a new list and Pass every value of the original list to the contains () method on a new list. How to remove duplicates from a list based on a custom java object not a primitive type? Circlip removal when pliers are too large. The equals method will return true when this.i is the same as other.j and this.j is the same as other.i, and return false otherwise. Not the answer you're looking for? Java 8:How to remove duplicates from the List based on multiple properties preserving the order. Asking for help, clarification, or responding to other answers. US Treasuries, explanation of numbers listed in IBKR. How do you manage the impact of deep immersion in RPGs on players' real-life? Why do I need to override the equals and hashCode methods in Java? Java List is an ordered collection of elements that may contain duplicate elements. Particularly, I am interested in adjusting this solution which removes duplicates only based on id: Another variant by merely following @Holgers approach would be. @shmosel Oh Maybe in multiple streams then? It then follows that constructing a set of size n has time complexity O(n log(n)). For example: "Tigers (plural) are a wild animal (singular)". In the circuit below, assume ideal op-amp, find Vout? Specify a PostgreSQL field name with a dash in its name in ogr2ogr, My bechamel takes over an hour to thicken, what am I doing wrong. rev2023.7.24.43543. Is not listing papers published in predatory journals considered dishonest? 3 Answers Sorted by: 35 You could filter them out and generate a unique Set: Set<Person> set = persons.stream () .collect (Collectors.toCollection ( () -> new TreeSet<> (Comparator.comparing (Person::getName)))); Or even nicer: Set<String> namesAlreadySeen = new HashSet<> (); persons.removeIf (p -> !namesAlreadySeen.add (p.getName ())); Is there a word for when someone stops being talented? Are there any practical use cases for subtyping primitive types? Otherwise the result.contains step will not work correctly. When to use LinkedList over ArrayList in Java? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Run 2 pointers and remove the duplicates manually by running 2 for loops one inside the other like we used to do in C language for arrays. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing. I would consider this approach inappropriate for a single use case, unless the rules of the object were consistent and allowed for. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. It would help also if you posted the code for the overridden equals and hashcode methods. English abbreviation : they're or they're not. Connect and share knowledge within a single location that is structured and easy to search. ..but the this way the first match will be kept in employee. To remove duplicates use distinct method. If there are employees with the same name, the 3rd argument (which is a binary operator), selects the employee that has max age. (Bathroom Shower Ceiling). How to remove duplicate elements from list of object. It is obviously not feasible for the entire stream op to keep the names of 100 million entries 'in memory'. In particular, what happens if you have 3 Sam students and each record has studentAttendence = 100? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. LinkedHashSet preserves ordering while HashSet does not. How do I avoid checking for nulls in Java? The datastructure (a List) also does not offer any fast lookups; there is no way to write code that answers the question 'how many records with studentName Sam is in this list?) HashSet<Object> seen=new HashSet<> (); customers.removeIf (c -> !seen.add (Arrays.asList (c.getName (), c.getDayOfBirth ()))); To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Unrelated to your direct question, perhaps consider using a Set instead of List if you want to avoid duplicates in the first place. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. I have list of obj1s filled with data where I need to extract it with some filters. This function creates a List of field values and this List act as a single key for that Stream item. Remove duplicates from java list without using sets. distinct - Returns a stream consisting of the distinct elements (according to Object.equals(Object)) of this stream. What's the DC of a Devourer's "trap essence" attack? In that case you can use a stateful anyMatch:. 592), Stack Overflow at WeAreDevelopers World Congress in Berlin, Temporary policy: Generative AI (e.g., ChatGPT) is banned. If all records have an attendence of 100, keep them all, then: Will do the job, and will do it quickly. My bechamel takes over an hour to thicken, what am I doing wrong. A LinkedHashSet, on the other hand, is an ordered collection of unique elements. Is this mold/mildew? One way is to group the objects based on keys (requires correct implementation of equals and hashCode methods for Order): Since you need to collect duplicates only for elements which have status == COMPLETED you could use a map with an appropriate key. Can a Rogue Inquisitive use their passive Insight with Insightful Fighting? Improving time to first byte: Q&A with Dana Lawson of Netlify, What its like to be on the Python Steering Council (Ep. I need distinct values of this combination: id, value and status = COMPLETE In order to use distinct your object needs to implement equals method. Connect and share knowledge within a single location that is structured and easy to search. Its purpose is to create a map in which keys will be generated by the given keyExtractor function, and values will be represented with the Deque of elements (this data type was chosen in order to facilitate the convenient access to the most recently added element). That's very strange, and probably not what you intended. Conclusions from title-drafting and question-content assistance experiments Java List, Keep First Item, Remove Second Duplicate, Remove duplicates from a list of objects without relying on a set. How can I remove all duplicates from the list based on the name property and to keep in the output the entry with the largest age? Term meaning multiple different layers across many eras? Why would God condemn all and only those that don't believe in God? All you need is filter and flatMap to get the duplicated objects into List. If you "map" any COMPLETED status to just that and any other status to new Object() you will effectively have equal keys for orders with the same id, name and status COMPLETED and unique keys for those with any other status (because Object.equals() uses instance identity only). Getting Distinct Stream Items by Comparing Multiple Fields - HowToDoInJava Do I have a misconception about probability? The distinct() method of the Stream returns a new Stream of unique elements. If I understood your goal correctly, you want to remove only elements having a value of null if there's at least one more element that has the same name.. public List<DataClass> removeDuplicates (List<DataClass> dataList) { List<DataClass> resultList = new ArrayList<DataClass> (); // Convert array list to Linked list LinkedList<DataClass> linkedList = new LinkedList<DataClass> (); for (DataClass obj: dataList) { linkedList.add (obj); } // Iterate through linked list and remove if values a. 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