Fastest way to compare two lists java. This will be the fastest way to compare two files.

Fastest way to compare two lists java g. Use Collection#retainAll(). Learn compare, find commonality, and difference in two Java Lists using Plain Java, Java Streams, and Commons Collections library Java provides several techniques for comparing two lists and finding the elements that differ. List<Item> list1; List<Item> list2; boolean anyMatch = list1. Stack Overflow. anyMatch(x -> What's the quickest to compare two strings in Java? Is there something faster than equals? EDIT: I can not help much to clarify the problem. You wouldn't have to use loops at all. I am looking for the fastest way to output the index of the first difference of two arrays in Python. Share. The List. MyData { String name; boolean check; } ListA and ListB both contains MyData objects ,now I have to compare both the list's object values here name as well check This is what I have tried and somehow I get the feeling that this is not right or this is not the best performing application, so is there a better way to do the searching and fetching the duplicate values from a Map or as a matter of fact any collection. asked Apr 2, 2013 at 12:33. How compare numbers in javascript. Compare two lists of string using java stream. How to compare two large array lists efficient in java. ) This is straightforward for integers: sorted(a) == sorted(b) It gets a little trickier with arbitrary objects. You can convert this Set back into an (Array)List if you need to at the end. Here the ElementRangeIndex is a bean class which contains some string values. This will be useful if order doesn't matters What's the fastest way to compare two large lists of 1's & 0's and return the difference count/percentage? Ask Question Asked 13 years, 9 months ago. List(1) = "foo, foo1, foo2, foo3" List(2) = "foo, foo1, foo2, foo3" When comparing these two lists if ALL strings match then the method returns true. In this example, we have created two ArrayList firstList and secondList of String type. The following Java program tests if two given lists are equal. A simple way to do that is to override equals and hashCode. Best Practices, Java Basics, Java Loops, Java Performance. Viewed 9k times 6 . October 16, 2022. Also for those that are unfamiliar: the final modifier just affects the reference to the list object For each ArrayList<Widget>, add each element to a Set<Widget> (HashSet or TreeSet, depending on whether they can be ordered in some way, or are hashable) utilizing addAll. 347 2 2 gold badges 5 5 silver badges 14 14 bronze badges. How could it be in the list and not be in the set containing the same elements as the list (only one time rather than several)? – Over at CR, this might fit the Not As Easy As It Looks category (especially with a non-symmetric compare and general java. Basically, it sorts the arrays, then pass through each one, adding ones that don't match to the LinkedList at each opportunity, then makes an array at the end. 2, java. 100 elements will get sorted extremely fast in any slightly modern machine. Which is the most efficient way of comparing large number of value which are stored in array? 2. import org. In Java, is it faster to iterate through an array the old-fashioned way, for (int i = 0; i < a. Commented Jan 9, 2013 at 14:07. If both lists are unequal, we will find the difference between the lists. Checking the number of keys is a way to do it, but I'd do it before comparing values. Starting with compare every item in [a List L] with every other item in [L] – You may say "But it is much faster to compare strings - no loops" well, then you should note there ARE loops. We are working on performance optimization in our app at the moment, so this question is The problem is this: I have two different lists that have thousands of elements. euqals(l2),and so on But it seems not the effective way,It cost about O(n^2), and that there are not Two List,It may be three or Fastest way to check if a List<String> contains a unique String. Mark and SilentGhost generally tell you how it should be done in a Pythonic way, but I thought you might also benefit from knowing why your solution doesn't work. isEqualCollection(joinedFnlData, joinedFnlDataTMP); I have two lists List listOne, List listTwo, and i want to compare both and if both are same i want to add the list item into some other list ol1 else add to ol2. Note that we are also comparing a list of B's for A's in both lists, so if there is a matching A's, but there is a delta of their B's, we should be able to add it to existingList's A's bList. Anyway I've pinpointed the bottleneck down to the call to What's the fastest way to concatenate two Strings in Java? i. You can do something like the functional java List. Or, you could use an explicit iterator for both. equals() to tell if they are different and then get the keySet of each hashmap and compare them: What is the fastest way to compare two sets in Java? Then once you've got the differences in keys, you could repeat the process on your value collections. 1. While access to the ArrayList is O(1), creating it is not as simple, because of dynamic resizing. There a significant number of them, many with similar characteristics. Lets say we have the following function to copy one ArrayLis Java provides a method for comparing two Array List. And I created another arrayList equal to the size of first list I have just started working on powershell. html html files directly as they are. I have solved this using the following algorithm and it works, BUT the problem is that if I have a large list it takes too much time to compare the entire list to print out the first position of the unique word. I started my project with googling "How to compare images using java" and I got some good articles on finding the similarity of two images. Note that this is generally the That's definitely Java 8 way. Assuming you mean that you want to know if the CONTENTS are equal (not just the list's object reference. The list is a linkedlist of type Map <String, The most efficient way to compare two List of Map to identify the matching and non matching records with multiple filter predicates in Java8 Streams is: Java Compare Two Lists. The code would be very large to compare every field and multiplied by different entities I want to compare two tables with million of records in each table and get match data from the comparison. asList(1,3,5); List<Integer> list2 = Arrays. The strings are fairly short being 15-25 characters long. I hava to compare two Or more Set like List'<'Integer'>' l1,List l2,List l3 ,But How to compare them ? In my view,first Collections. Edit to summarize comments. I have two String which are sorted alphabetically and EXACTLY the same size. But, maybe I misinterpreted. Java compare two lists efficiently. What I need to do is loop through them and find which list item is newly added and which one was deleted. Java Collections . " Best way to compare 2 lists. About; Products OverflowAI; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent About java. First recursive loop that converts Array to string and second, that compares two strings. May or may not be an issue. append(StringBuilder. – This could be done in a lot easier way if you could implement the equals method in your TestClass. They contain objects of different types, but both types contain id and name, and id is what I am comparing on. That being said, I think your approach is pretty close to standard, and I wouldn't worry about trying to optimize it unless you really end up needing it. I want to check if both lists contain the same element and if soo i want to add that element in a separate list. In both cases they also check order. Fastest way to compare a number to a list of numbers in a range? 0. (one of the array's is temporary array) java; arrays; compare; Share. imagemagic tool does this for me using cmd prompt. so comparisons between 1 and 1 is true, -1 and -1 is true, 0 and 0 is true, 0 and 1 is false, 0 and -1 is false, etc. length(); final int maxlen = Integer. I believe that larger amounts of data should be always stored in arrays, not in objects. Then, if the first name in both lists is the same I want to compare if any of the objects in a list2 is present in a list1. Some of them are using : Stream API; ListIterator interface; Enhanced for-loop; I want to know what would be the fastest way to compare 2 objects in java 8. Strings can be long up to 30 characters Note: This is much more efficient than naively doing the intersection with two lists: it's O(n+m), versus O(n×m) for the list version. Sort then Compare. of( "Bill" , "Steve" , "Mark" ) . I have two ArrayLists of type Answer (self-made class). Hot Network Questions Which French word for scarf is the In Java, "In other words, two lists are defined to be equal if they contain the same elements in the same order. Im trying to match every 400 000 items by name in another list where i could find the There's no faster way to prove that two files are identical than comparing them byte-for-byte (duh), but for typical files there are probabilistically faster ways to prove that they are not the same. I finally want to print list_out1 and list_out2. !! java; xml; Share. Comparing individual elements of two different arraylists? 1. Can't tell if it's the fastest way to compare objects/arrays, but it's faster than JSON. This buys you a faster O(n log n) performance, but still behind the HashMap/HashSet version You just need two sliding windows into your data strings. equals() and CollectionUtils. These classes supplant the troublesome old legacy date-time classes such as java. Is there a faster way to compare two Int arrays in Java? 0. private List<MembeAuditsResource> memberCompare(Member obj1, Member obj2) { //Compare every field in both the objects using if else and populate the resource. community wiki 2 revs, 2 users Why Compare Two Lists? There are many scenarios where comparing two lists is essential: Data Synchronization: Finding which elements are missing or extra in a list during synchronization. When i try with a small amount of elements in the lists, the program works perfectly fine but when i try with more elements, i have to wait for hours to get the right answer. In this quick tutorial, we’ll learn how to find the differences between the two lists. This is not the same thing as the For example: if I have a list: ["Hi", "Hi", "No"], I want to print out 2 because "No" is in position 2. 11. join(fnlDataTMP); CollectionUtils. Since I assume the equality between Person must also consider the id field, you can wrap this instance into a PersonWrapper which will implement the correct equals and hashCode (i. However I have two lists with different objects in them. @siride no prob. If you get to the end of both files without detecting any differences, seek to the beginning of file 1, close file 2 and open file 3 in You shouldn't use this method when using LinkedLists. What do you think? – Ankush. That is, let A be the smaller of the sets and B be the larger set and then, for each item in A, if it also exists in B then add it to C (a new HashSet) -- for just counting, the intermediate C set can be skipped. Please suggest I have two collections. length; i++) f(a[i]); Or using the more concise form, for (Foo foo : a) f(foo); For an . I have two lists. Ask Question Asked 14 years, If the type of items is primitive or wrapper, you may not care. I have previously done this: str1 === str2 , but I wonder if there is a faster way to compare two strings. But if it is a class, you must override two methods: hashCode() equals() Share. That's a performance question IMHO. 7. I am interested in knowing the answer as I am trying to find the fastest way to compare two lists of the same length (around 2000 or so, where each element is a unique string. Now just because this is the fastest algorithm in finding if all elements equal a value doesn't mean you have optimized it Failing fast at scale: Rapid prototyping at Intuit Java :Comparing two lists. Fastest way to compare two lists. Sample Entity: @Entity public class NormalBook { @Id private String bookId; @Column private String title; @Column private byte[] pdfFile; //setters and getters } Brute force searching arrays. size()); listB Efficient way to Compare Two List's object values without implenmenting What is the quickest (and least resource intensive) to compare two massive lists (>50. u1 see Fastest way to compare strings (literal and numerical) Ask Question Asked 15 years, 4 months ago. com Java Tutorials for Freshers and Experience developers, Programming interview Questions, Data Structure and Algorithms interview Programs, Kotlin programs, String Programs, Java 8 Stream API, Spring Boot and Troubleshooting common issues. Given another arbitrary number x, what's the fastest way (on average) to generate the boolean value of whether x is contained in the set or not? The probability for !contains() is about 5x higher. It really doesn't matter: honestly, just pick one. 3. Finding differences in two lists. Follow asked Sep 4, 2012 at 18:41. You may not be able to modify an instance of the CompositeUnmodifiableList itself but if you can get a reference to the original lists, then you can. equals(), if they are List<>s then you cannot just use equals. Shortest way to compare two arraylists. 6 standard library features, I'd prefer not to implement a hybrid class that emulated something from List and then Set for example. Sampling the beginning and end of the files first would find differences faster if the files are mostly the same, but different in only one part (usually the beginning or end). This algorithm is O(n) which is the fastest way to check all elements of a list because you only have to check each element only one time. In this blog, we’ll walk through various methods to find the differences between two Sort both lists with an efficient sorting algorithm (or ensure that the lists are "pre-sorted" by whoever/whatever created them). startDate >= now, call First of all: in order determine the intersection of two sets, you absolutely have to look at all entries of at least one of the two sets (to figure whether it is in the other set). activated && foo. listA. Instead, you could store the current index of the two Lists and compare the elements at the the indexes each time to merge in O(N) time complexity overall (taking advantage of the fact that both Lists are already sorted). equals() method returns true for two list instances if and only if: both lists are of the same size From Java 1. This runs in O(n log n + m log m), where n is the size of first, and m is the size of second. I have two ArrayLists that I want to compare and remove duplicates from each of them. Hot Network Questions 100 elements isn't a large set unless your comparison step is really heavy (doesn't seem like it). List one is fetched from DB, and list two is sent from frontend. File Programmatically. I found this and I am trying to implement the suggested method: . join method to quickly generate 2 Lists and compare these:. We have created a static method compareList () which parses two ArrayList ls1 and ls2 as an argument and returns a boolean value. So, size of first list is 4 and second is 3. The first way to use Set: Create a Set containing an intersection of both lists. I have 2 objects of the same class with 100 properties. I have a method to extract the values from an object collection that is a employee information: public class Employee { public String AREA; public String EMPLOYEE_ID; public String Using a DirectByteBuffer will only add value if the underling InputStreams are FileInputStreams and able to move data directly from file into the DirectByteBuffer without the memory having to go into jvm managed memory. The way that Map. I have a performance problem related to string comparison (in Java). collections. the length of arrays is the same. After that I can compare them the way I mentioned above. Comparing Two Lists for Equality 1. . My approach is to have a method that tells me whether those two lists contain the same entries with the same IDs. Modified 11 years, 7 months ago. Right now I have a brute force approach of iterating each ite I'm trying to compare two lists of type strings using equal method. The OP doesn't count the number of times an element is contained in the list. is there a faster way to extract unique values from object collection? Ask Question Asked 11 years, 5 months ago. The problem is that as soon as you find the first common element in the two lists, you return that single element only. I. While comparing the two lists it needs to compare each string value from the bean. I could iterate over both lists and compare all elements using . If you just want a count of one or zero, for a first match found or no match found, make a stream from the first list, filter with a predicate testing if the second list contains each streamed item from the first list, limit to the first match found, and returning via a ternary statement either number 1 or 0. time. Is there a way to compare two Your current algorithm has a running time of O(n*m), for two lists of sizes n and m. Note that as you're treating these in a set-based way, I'd suggest using a set implementation such as HashSet<E> instead of lists. Of course, you could also use removeAll, which will leave you a List on non This is a workable solution, but do note that if the underlying list objects change (list1, list2), the contents of this list change. To get the match data from both the tables we are first comparing the name in table1 should not be equal to name in table2. CollectionUtils; List listA = ; List listB = ; Collection intersection = CollectionUtils. In C++ std::list is a doubly linked list. The best way to do this is by sorting the lists and comparing them. The method converts a list into String. It's not the only way possible of sorting ranges, but its the one I think would be most useful in this scenario. It compares the Array lists as, both Array lists Explore various methods to compare and analyze Java lists, including sorting and using built-in methods like List. length(); i < n; i++) { char c = str. join(fnlData); List<String> joinedFnlDataTMP = jf. It may not be the perfect way, but I am still This Java article compares the performance of an ArrayList iteration using simple for-loop, enhanced for-loop, list iterator and stream API. Among the more popular: Levenshtein Distance: The minimum number of single-character edits required to change one word into the other. ; Filtering: Removing or processing only the elements that differ between two lists. Also you can speed up the process by setting depth limit. Viewed 23k times 4 . List<>. Then we are comparing city in table1 should be equal to city in table2 and then finally we are comparing date_of_birth in table1 should be With that in mind, I would like to know the fastest way to compare these two list of A's, and add the delta of these two lists to the existingList. Comparable interface allows comparison by one field only; Adding numerous compare methods (i. Sets contain no duplicates by default. equals() is the method used for comparing two Array List. What is the best way to combine two lists into a map? It would be nice to use for (String item: list), but it will only iterate through one list, and you'd need an explicit iterator for the other list. If you want to avoid that changes are being affected in listA, then you need to create a new one. assertTrue(listA. 45. You can implement a Comparator which compares two Person objects, and you can examine as many of the fields as you like. In Java, what would the fastest way to iterate over all the chars in a String, this: String str = "a really, really long string"; for (int i = 0, n = str. I also think it is faster to compare (many) smaller files to each other than those two huge files. Commented Aug 28, 2017 at 20:54. isArray a bIsArray = Array. Akhil Jain. Yes, I use Java as my programming language. Modified 10 years, 11 months ago. contains() but I am wondering if there is not a more efficient way. intersection(listA, listB); Important: Start by selecting "Instagram followers" to remove unwated data like dates and profile picture texts from the lists. Wild guess here, but I don't think there is going to be much difference, since computing the hash itself is roughly as costly as doing the direct string compare, and you may have to deal with collisions. asList(1,2,3,4,5); ArrayList<Integer> list2Copy = new ArrayList<>(list2); So to compare two files, use this algorithm: Compare sizes; Compare dates (be careful here: this can give you the wrong answer; you must test whether this is the case for you or not) Compare the hashes; This allows for a fast fail (if the sizes are different, you know that the files are different). We will also learn to find common as well as different items in each list. I'm working on a project that needs to sort a huge list (a TableViewer in Eclipse). I need to compare the list of strings with a field from the class and remove duplicates from the list containing the class. To test equality, we need to sort both lists and compare both lists using equals() method. ; Validation: Ensuring that 1. Java . Learn to test whether two arraylists are equal and then find different list items. When using linked lists it's highly Here I am trying to compare two lists of string. import java. retainAll(outList) will return you a List which contains all the objects from inList which are in outList, use outList. 5. java. List A comes from 1 system. Java provides a method for comparing two Array List. Also, comparing simple equality would not be enough: as I've said, dictionary keys are based on identity, and that makes using === a necessity. The solutions suggested by S. Modified 11 years, 5 months ago. – Louis Wasserman. How do I compare the performance of two similar bits of code? 1. I am trying to find a method for comparing two lists in python in a more efficient way than what I think is the current O(m*n) runtime. The comparison I need is to compare the first item in List 1 with the first item in List 2, the second item in List 1 with the second item in List 2, and so on, and returns a result if ALL of the list items follow the same comparison criteria. I have two strings and I need to know whether they are equal. See more linked I want to compare these two lists. – Nick Ryan. List<CustomObject> firstList; List<CustomObject> secondList; Edit: I realize there is a similar problem found here: Fastest way to check if two integers are on the same side of 0 I am asking if there is a way to find if signs are the same INCLUDING zero. String class implements its hashCode() using a product sum algorithm over the entire text of the string. 0. What is the fastest way to find the properties which have different values apart from the compareTo() method in which they are checked for the properties one by one. Now I wonder, if there is a more direct or more efficient way of doing the comparison using other Java 8 statements, for example allMatch() or some Predicate<T> or something else. You can pre-sort the lists in O(nlog(n)+mlog(m)) time, and then iterate once on both lists to find elements having the same name (that iteration would take O(m+n)). So what is the best way to go This is a workable solution, but do note that if the underlying list objects change (list1, list2), the contents of this list change. Or just use FileUtils. Also for those that are unfamiliar: the final modifier just affects the reference to the list object One of the possibilities worth considering is to create Set<String> and add these lists to it. hashmap and list compare. I only used characters for the sake of the example). If any of the element matches, in the first match, increment the count, add matched value to matchList and break the loop. Strings do not have to be the same length; Hamming Distance: The number of characters that are different in two i got two String type arraylist . JavaProgramTo. For example, let's take the following two arrays: test1 = [1, 3, 5, 8] test2 = [1] test3 = [1, @Radiodef I would answer but the question is not yet clear. *; public class ListsToMap { static public Learn to compare two ArrayList in Java to find if they contain equal elements. int count = List. Storing the two columns in two different arrays. class PersonWrapper { private Person person; private PersonWrapper(Person person) { this. You can then paste your copied lists or you can upload the exported following. Example: abbcee and abcdee. It compares the Array lists as, both Array lists should have the same size, and all corresponding pairs of elements in the two Array lists are equal. There is no magic around that would tell you that in less than O(min(size(s1), size(s2)). When I profile then this is the bottleneck. util. only check the name and age fields):. My problem is that I am iterating through a lot of strings and it is taking quite a long time. user1633823 user1633823. From Java 1. Improve this answer. Rohit Jain. They have 85 records in common and I want to get the values which are in list1 but not in list2 in a seperate list say list_out1 and the values which are in list2 but not in list1 in another list say list_out2. 213k 45 45 gold badges 414 414 silver badges 533 533 bronze badges. You can use equals with map as well. } And then calling the above function to compare every pair of record in the entity_audit table. I have two lists in java where I need to remove duplicates. cmp = (a, b) -> (a > b) - (a < b) cmpArray = (a, b)-> aIsArray = Array. How to compare two ArrayList in java. Watch this video on Youtube to see how it can be done. io. min(s1len, s2len); // from the longest overlap to the What you're looking for are called String Metric algorithms. java:93) In Java, there’s no explicit way of finding the differences between two lists in the List API, though there are some helper methods that come close. Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company I'm guessing the original poster is coming from a C++/STL background which is causing some confusion. It checks if it's in the list or not. retainAll(listB); // common now contains only the elements which are contained in tl;dr. (Maybe for lists with between 0 to 5 elements I'd guess. As such, you might be tempted to sort your data first, placing duplicated elements near each other. Viewed 1k times 0 I am looking for a better way of comparing two "lists". Here is I would like to know what is the best, fastest and easiest way to compare between 2-dimension arrays of integer. stream() . java; Share. NOTE: Both functions are depending on each other. contentEquals(file1, file2); from org. e . Compare the two ArrayLists in java which contains same objects. equals() works is by comparing keys and values using the Object. Set allows adding only unique values to itself, it prevents adding duplicates. If they match, read the next block from each, compare them byte-by-byte, etc. This means you cannot meaningfully compare two objects of this class, so it is not possible even in principle to do what you are asking. We have compared these ArrayList using contains() method. I'd opt for something like the approach taken by the cmp program: open two files (say file 1 and file 2), read a block from each, and compare them byte-by-byte. Note that the difference between two lists is equal to a third list which contains either additional elements or missing elements. The Sets class in Guava provides useful methods for working with sets. This buys you a faster O(n log n) performance, but still behind the HashMap/HashSet version You are right in saying that if they are arrays you can't use Arrays. Lokesh Gupta. My natural way would be to test first for the start agains start, and then end against end. retainAll(inList) for the reverse. e. 2k 15 15 gold badges 60 60 silver badges 94 94 bronze badges. Assume Widget has an overridden equals method that can be used for determining whether Fastest way to check if value is in array many times. startDate >= now, call Just use a byte comparison with BufferedReader. retainAll(listB); // listA now contains only the elements which are also contained in listB. Follow edited Sep 24, 2018 at 20:27. So yes your main option without writing your own comparison algorithm is to use Collections. Example: Input : ArrayLis I have two collections of the same object, Collection<Foo> oldSet and Collection<Foo> newSet. lang. First check if the file length is the same. The contents of each list item is either 1 or 0 Brute force searching arrays. mee Now my query is please advise is there any other way which is fastest to read this xml , I was looking the fastes , Please advise. Java provides many ways to iterate over a List. It returns true if the element is matched, else returns false. /** * @author aupanner */ public class Overlap { static int calculateOverlap(final String s1, final String s2) { final int s1len = s1. Is the OP wanting to test whether the two lists contain the same elements according to the Comparator (as JBNizet has assumed), or is the Comparator just a means to testing whether the two lists contain the same elements with respect to equals?In the question, the OP sorts the lists using the Comparator Run some tests with the posted approach and versus constructing a new HashSet. You have not specified what it means to "compare" two lists, and what is meant by the "delta". The performance difference is unlikely to matter, so pick whichever one reads best to you. One way to do this is to first create a copy of list 2 called list2Copy, then remove all the elements in list2Copy that does not exist in list1. Why Compare Two Lists? There are many scenarios where comparing two lists is essential: Data Synchronization: Finding which elements are missing or extra in a list during synchronization. We’ll try a few different approaches, including plain Java (with and without Streams), and third-party libraries, such as Guava and the @siride, Bunyip asked what the fastest way was to compare two lists. I am looking for more efficient way to compare this collections and to get results: List of cars which are in newCars and not in currentCars Comparing two Lists - looking for faster and more efficient way. ; It should be benchmarked to know for sure. Improve this What is the fastest (performance) way to compare if a string is present in a large list I have a situation where I will be receiving 2+ ArrayList<Widget> and I need to be able to merge all the lists and remove any duplicate Widget so that I wind up with only 1 ArrayList<Widget> that contains all Widgets from all the merged lists, but without any duplicates. To compare the two nested objects we need to do the following steps : Can't tell if it's the fastest way to compare objects/arrays, but it's faster than JSON. length(); final int s2len = s2. Each iteration the get method will iterate from the beginning of the list to the current element, which leads to O(n²) asymptotic performance. Note you will need to implement hashCode for your Widget class if I hava to compare two Or more Set like List'<'Integer'>' l1,List l2,List l3 ,But How to compare them ? In my view,first Collections. Commented Aug 28, 2017 at I came across a question related to ArrayList of java in a company written test. SequenceEqual is fast to write but may become very slow to execute. Related. Adding to new, getting rid of duplicates lists is taking place only if you checked that every object of the source is not present in This is basically the same algorithm avoiding the typeof operator and doing a little trick in the for loop to not check for the lengths of the arrays every time:. Lists are re-sizeable. If you do, use ArrayList; it will certainly be faster. Discover how to find additional items, In Java, there’s no explicit way of finding the differences between two lists in the List API, though there are some helper methods that come close. html and followers I have a function wherein i need to check if data matches in two lists. The array will almost certainly be faster. java:119) java. ) For medium to large sized lists you can either: sort the both array lists and compare them pair-wise, sort one list and use binary search to This method parses an element whose presence in the list is to be checked. The first So my question is, is there an easy way to remove the duplicated elements from both ArrayLists? If so, how do I go about it. Follow edited Apr 2, 2013 at 12:44. size(), listB. euqals(l2),and so on But it seems not the effective way,It cost about O(n^2), and that there are not Two List,It may be three or Java provides a method for comparing two Array List. In the example above, the list of persons (or people) is transformed to a list of Strings using Java 8 techniques and the comparision is done in the old-fashioned way. If the elements of firstList match with the elements of the secondList, it return Yes and Removing from the front of an ArrayList has O(N) time complexity since all other elements need to be shifted. E . Example: Input : ArrayLis No, it can't be different. sort(list),then l1. 14. asked Mar 31, For very small lists, using contains() is probably most efficient. My method returns true if all Strings from both lists matches. This is a great way of doing it, but if I want to match the contents of the file line by line, and then print the matching name and id each from the 2 files How to compare two java. 1. After watching the first 2 minutes, just use following. Compare two arraylist. Otherwise, you'll probably have to profile. concat is faster than the + operator if you are concatenating two strings Although this can be fixed at any time and may even have been fixed in java 8 as far as I know. Using an ArrayList will bring the performance more in-line since it's backed by an actual array. (Using Counter won't work with objects that aren't hashable. StringBuilder. Period. 2. I want to use the fastest possible method to match a String with a String in List. I am looking for a better way of comparing two "lists". commons. 6. a button's position is different) and output the result image in new gif image which highlights the difference. And a better way to traverse through a collection. So this method is faster than use of string. List<Car> currentCars = GetCurrentCars(); List<Car> newCars = GetNewCars(); I don't want to use foreach loop or something because i think there should be much better way of doing this. Im iterating trough a list to match productname and set price for that product. one list containing “book1”, “book2”, “book3” and “book4”. compareByFirstName(), compareByAge(), etc) is cluttered in my opinion. List<Object1> list1; List<Object2> list2; I want to check if element from list1 exists in list2, based on specific attribute (Object1 and Object2 have (among others), one mutual attribute (with type Long), named attributeSame). Just as the posted approach, this should be a O(|A|) in cost as the iteration is O(|A|) and probe into Recently I got an opportunity to work with Image Processing Technologies as a part of one of my projects and my task was to find matching images from an image store when a new image is given. You just need to define a proper way to compare ranges. Learn what is the fastest way to compare two sets in java 8 . This will be the fastest way to compare two files. The Learn to compare two arraylists in Java with List Items. I realize that I could probably deep clone the updated ArrayList and just remove the objects from that one, but I'm wondering if there is a way without having to clone it You can't just use the keys from d1, because there might be more keys in d2, and then they still wouldn't be equal. If you don't need to check for duplicates you could drop both lists into a HashSet using addAll and I don't think there is a way that let's you achieve that out of the box. By adjusting the width of the window, you determine the overlap. Do all the map structures provide o(1) operation? Is HashSet the fastest way to go? You shouldn't use this method when using LinkedLists. And another arrayList contains “book1”, “book2”, “book3”. About; Products OverflowAI; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & I have two list **ListA<MyData> listA = new ArrayList<MyData>()** and ListB<MyData> listB = new ArrayList<MyData>() both contain object of type MyData and MyData contain these variables. isArray() but I like to compare two images. What is the fastest method to compare two large files in Java. Here's an example of the problem, and a solution using an indexed for loop instead:. List B comes from a SQL table (I can only read, no stored procs, etc) What Best way to compare two large string lists, using C# and LINQ? Ask Question Asked 14 years, 11 months ago. The java. time framework is built into Java 8 and later. Now you just need to compare if they are exactly equal to each other. person Off the top of my head, you could first use HashMap. fast and xml generally don't go together. I'm currently looking through two very large lists of Peak Objects, by overriding the equals method and looping through the two lists, comparing every peak to every other peak. String ccyPair = ccy1 + ccy2; I'm using cyPair as a key in a HashMap and it's called in a very tight loop to retrieve values. It's possible. List(1) = "foo, foo1, foo2, foo3" Given a list of KeyValuePairs, where each pair has a getValue() method, what would be the fastest way to obtain a List (or Set) of unique Values? All of the below produce acceptable result. (StringBuilder. find the delta between the new list and the old list, Java: Difference between two lists. inList. I'm in need of a method to quickly return the number of differences between two large lists. Compare two Lists for differences. To learn more, see the I'm trying to compare two lists of integers, each the same size, in Python 2. the fastest possible way of achieving my two goals, whichever the case; using only Java 1. filter( ( I want to compare the content of two Lists, in particular a certain method of the custom object stored in both of these lists, let's call it #getID(). Match strings in two lists in Java 8. Viewed 8k times 2 . 6. Re-read my comment. List<Integer> list1 = Arrays. FileUtils. Is there a more efficient way of doing this? My lists can be ~10,000 elements, which means up to The List equals() method in Java compares two lists for equality based on their size and corresponding elements, returning true if they are equal. One list contains a class (UrlInfo) with three fields, the other contains a list of strings. I have two lists of 132 and 134 records each. However i want some tool which generate the new image like this however only if there is a difference. List<Integer> common = new ArrayList<>(listA); common. Example. Read a byte block from one file and compare it with the byte block of the other file. List. List<String> joinedFnlData = jf. isArray b return cmp a, b if not aIsArray and not bIsArray return -1 if not aIsArray and bIsArray return 1 if aIsArray and not It depends largely on whether you know the maximum size of each list up front. What's the most efficient way to compare values of two objects? Hot Network Questions What’s a bug breach in Helldivers 2? What does the MUX (4P2T) in this I have a large list (~ 110,000 strings), which I need to compare to a similar sized list. Not at all. ) If you will be doing the equality check much more often than inserts then you may find it more efficient to generate a hashcode each time a value is inserted and compare hashcodes when doing the equality check. I need to fetch the two list values from some table. sort() on both lists. stream(). apache. Thank you to all of those who reply in advance. Follow edited Dec 13, 2012 at 13:19. EDIT I now divided the huge files first so that I have no problems with being out of memory. Improve this question . The code may overwrite some of your methods! Well, if you used a LinkedList, the memory would be such an issue, as you are only maintaining references to the objects, not new copies ;). With two million-item lists it's the difference between millions of operations and trillions of operations. I have got two java objects with byte[] field of the size of the order of millions. The code may overwrite some of your methods! /** * works like Array. FIrst, and MOST IMPORTANT, note that your AddressInfo class does not define an equals() method. This definition ensures that the equals method works properly across different implementations of the List interface. My query is just a small part of the actual question. The earlier revision of this code did not work correctly because the trailing elements in the longer list were not getting From Java 1. data. html and followers. The idea is : I have 2 lists which are composed of Strings. When using linked lists it's highly Both the values are equal but how to compare them in java? We have equals and equalsIgnoreCase for comparing String alpha values, similarly how to compare numeric values. You can put in a variable in your comparator that tells it which field to compare to, although it would probably be simpler to just write multiple comparators. text processing is inherently Your question is incomplete. Ask Question Asked 10 years, 11 months ago. Modified 1 year, 11 months ago. isEqualCollection(). Using Java 7 API to read a file byte by byte-2. Modified 7 years, 7 months ago. stringify() comparison. I assume its performance would be slower than Option 1. ; Validation: Ensuring that the data in two lists match or identifying discrepancies. equals() method. The next thing to tell the interviewer: "1 million entries. Skip to main content. The thing you missed in the first post you referenced is that the author is concatenating exactly two strings, and the fast methods are the ones where the size of the new character array is List<String> listA = new Arraylist(); List<String> listB = new Arraylist(); Given above 2 lists, I want to iterate and call the same method on each element. 000 items) and as a result have two lists like the ones below: items that show up in the first list but not in the second; items that show up in the second list but not in the first What is the cleanest way to enable multiple comparison between these kinds of objects without adding unnecessary clutter or overhead? java. Compare 2 java lists using custom logic. Is there some Java 8 lambda way to do this? Also, performance wise, would anything better than Option 1? Not sure if it's faster but does avoid defining an inner lambda as well as With that in mind, I would like to know the fastest way to compare these two list of A's, and add the delta of these two lists to the existingList. Create Extension function as below. Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company String. The required logic is as follow: if foo is in(*) oldSet but not newSet, call doRemove(foo); else if foo is not in oldSet but in newSet, call doAdd(foo); else if foo is in both collections but modified, call doUpdate(oldFoo, newFoo); else if !foo. I'd like to compare the two lists to see if they contain the same contents, but without Assuming if we can modify one list, with the support of java 8 removeIf. it compares two images (for e. Is there any fast method to do the same and also since in two lists the number of entries can be large, so I need to efficient method for doing so. In a simple, array based algorithm, where you search the entire array before inserting each element, you would get a very bad O(n²) performance. Another point to consider is that the space-time trade-off is not clear cut. Viewed 17k Rather than writing code to manually compare list elements you might consider using Apache Commons Collections. What is the fastest and efficient way to check Deep Equal for these java objects?. In Java [java. This means that (1-10) < (1-100) < (2-10) < (2-1000). Performance differences tend towards minimal. Date, Calendar, & SimpleDateFormat. The ArrayList. ]List is an implementation-free interface (pure abstract I have two collections of the same object, Collection<Foo> oldSet and Collection<Foo> newSet. compare 2 ArrayList java. jdcoz ogpdth kqtpsa gslu gres mnpjfkop fohdtd pbmyz hkkoyq zwg