sort list based on another list java sort list based on another list java

2023 DigitalOcean, LLC. It returns a stream sorted according to the natural order. Rather than using a list to get values from the map, well be using LinkedHashMap to create the sorted hashmap directly. Other answers didn't bother to import operator and provide more info about this module and its benefits here. Is it possible to create a concave light? In addition, the proposed solution won't work for the initial question as the lists X and Y contain different entries. In java 6 or lower, you need to use. This class has two parameters, firstName and lastName. What I am doing require to sort collection of factories and loop through all factories and sort collection of their competitors. The method returns a comparator that imposes the reverse of the natural ordering. Warning: If you run it with empty lists it crashes. From simple plot types to ridge plots, surface plots and spectrograms - understand your data and learn to draw conclusions from it. You are using Python 3. Overview Filtering a Collection by a List is a common business logic scenario. All of them simply return a comparator, with the passed function as the sorting key. This method will also work when both lists are not identical: Problem : sorting a list of Pojo on the basis of one of the field's all possible values present in another list. We first get the String values in a list. All of the values at the end of the list will be in their order dictated by the list2. @Hatefiend interesting, could you point to a reference on how to achieve that? But it should be: The list is ordered regarding the first element of the pairs, and the comprehension extracts the 'second' element of the pairs. They're functional in nature, and it's worth noting that operations on a stream produce a result, but do not modify its source. Sorting values of a dictionary based on a list. Do I need a thermal expansion tank if I already have a pressure tank? Java List is similar to arrays except that the length of the list is dynamic and it comes in Java Collection framework. Is there a single-word adjective for "having exceptionally strong moral principles"? Returning a positive number indicates that an element is greater than another. Lets look at a quick example to sort a list of strings. Create a Map that maps the values of everything in listB to something that can be sorted easily, such as the index, i.e. QED. This is an old question but some of the answers I see posted don't actually work because zip is not scriptable. Did this satellite streak past the Hubble Space Telescope so close that it was out of focus? We can also create a custom comparator to sort the hash map according to values. As you can see that we are using Collections.sort() method to sort the list of Strings. Using a For-Each Loop The java.Collections.sort () method sorts the list elements by comparing the ASCII values of the elements. Why does Mister Mxyzptlk need to have a weakness in the comics? Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? If you want to do it manually. String values require a comparator for sorting. Assuming that the larger list contains all values in the smaller list, it can be done. Once we have the list of values in a sorted manner, we build the HashMap again based on this new list. How is an ETF fee calculated in a trade that ends in less than a year? We will use a simple sorting algorithm, Bubble Sort, to sort the elements of a linked list in ascending order below. Two pointers and nodes make up a tree. This can be elegantly solved with guava's Ordering.explicit: The last version of Guava thas supports Java 6 is Guava 20.0: First create a map, with sortedItem.name to its first index in the list. The solution below is the most efficient in this case: Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. The solution below is simple and should fix those issues: Location of index in list2 is tracked using cur_loclist. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? Check out our offerings for compute, storage, networking, and managed databases. Here is Whatangs answer if you want to get both sorted lists (python3). The collect() method is used to receive elements from a stream and stored them in a collection. @Hatefiend interesting, could you point to a reference on how to achieve that? It puts the capital letter elements first in natural order after that small letters in the natural order, if the list has both small and capital letters. It would be preferable instead to have a method sortCompetitors(), that would sort the list, without leaking it: and remove completely the method getCompetitors(). The second one is easier and faster if you're not using Pandas in your program. The method signature is: Comparable is also an interface belong to a java.lang package. More general case (sort list Y by any key instead of the default order), http://scienceoss.com/sort-one-list-by-another-list/, How Intuit democratizes AI development across teams through reusability. This is an old question but some of the answers I see posted don't actually work because zip is not scriptable. The best answers are voted up and rise to the top, Not the answer you're looking for? If a law is new but its interpretation is vague, can the courts directly ask the drafters the intent and official interpretation of their law? Sorting Strings is a tiny bit different, since it's a bit less intuitive on how to compare them. What sort of strategies would a medieval military use against a fantasy giant? Theoretically Correct vs Practical Notation, Bulk update symbol size units from mm to map units in rule-based symbology. Does a summoned creature play immediately after being summoned by a ready action? You can create a pandas Series, using the primary list as data and the other list as index, and then just sort by the index: This is helpful when needing to order a smaller list to values in larger. Wed like to help. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Warning: If you run it with empty lists it crashes. Sorting for String values differs from Integer values. That's easily managed with an index list: Since the decorate-sort-undecorate approach described by Whatang is a little simpler and works in all cases, it's probably better most of the time. Collections.sort() method is overloaded and we can also provide our own Comparator implementation for sorting rules. Here we will learn how to sort a list of Objects in Java. As I understand it, you want to have a combined sorted list but interleave elements from list1 and list2 whenever the age is the same. All Rights Reserved. A tree illustrates a hierarchical structure in contrast to other data structures such an array, stack, queue, and linked list, which are linear in nature. I don't know if it is only me, but doing : Please add some more context to your post. The below given example shows how to do that in a custom class. We've sorted Comparable integers and Strings, in ascending and descending order, as well as used a built-in Comparator for custom objects. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Sort a list of Object according to custom priority of value in the Object JAVA 11, sort list of object on java 8 with custom criteria, Sort list based on specific order in java, (Java) Using lambda as comparator in Arrays.sort, How can I sort a list based on another list values in Java, Android Java - I need to sort a list based on another list, Intersection and union of ArrayLists in Java. Find centralized, trusted content and collaborate around the technologies you use most. Use MathJax to format equations. That is, the first items (from Y) are compared; and if they are the same then the second items (from X) are compared, and so on. If you have any suggestions for improvements, please let us know by clicking the report an issue button at the bottom of the tutorial. There is a major issue with this answer: You are inserting a reference to the object originally in listB into listA, which is incorrect behavior if the two objects are equals() but do not refer to the same object - the original object in listA is lost and some references in listA are replaced with references in listB, rather than listA being simply reordered. Why do small African island nations perform better than African continental nations, considering democracy and human development? This could be done by wrapping listA inside a custom sorted list like so: Then you can use this custom list as follows: Of course, this custom list will only be valid as long as the elements in the original list do not change. vegan) just to try it, does this inconvenience the caterers and staff? JavaTpoint offers too many high quality services. How can this new ban on drag possibly be considered constitutional? rev2023.3.3.43278. that requires an extra copy, but I think to to it in place is a lot less efficient, and all kinds of not clear: Note I didn't test either, maybe got a sign flipped. my case was that I have list that user can sort by drag and drop, but some items might be filtered out, so we preserve hidden items position. All rights reserved. http://scienceoss.com/sort-one-list-by-another-list/. In Java how do you sort one list based on another? The solution assumes that all the objects in the list to sort have distinct keys. People will search this post looking to sort lists not dictionaries. We're streaming that list, and using the sorted() method with a Comparator. P.S. Let's start with two entity classes - Employee and Department: class Employee { Integer employeeId; String employeeName; // getters and setters } class Department { Integer . - the incident has nothing to do with me; can I use this this way? Follow Up: struct sockaddr storage initialization by network format-string. If a law is new but its interpretation is vague, can the courts directly ask the drafters the intent and official interpretation of their law? Also easy extendable for similar problems! How can I pair socks from a pile efficiently? Once sorted, we've just printed them out, each in a line: If we wanted save the results of sorting after the program was executed, we would have to collect() the data back in a Collection (a List in this example), since sorted() doesn't modify the source. B:[2,1,0], And you want to load them both and then produce: This comparator sorts the list of values alphabetically. Then you can create your custom Comparator that uses the Map to create an order: Then you can sort listA using your custom Comparator. All rights reserved. We can use the following methods to sort the list: Java Stream interface provides two methods for sorting the list: Stream interface provides a sorted() method to sort a list. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup, Sorting Each Entry (code review + optimization), Sorting linked list with comparator in Java, Sorting a list of numbers, each with a character label, Invoking thread for each item in list simultaneously and returning value in Java, Sort a Python list of strings where each item is made with letters and numbers. Once, we have sorted the list, we build the HashMap based on this sorted list. You can do list1.addAll(list2) and then sort list1 which now contains both lists. In this quick tutorial, we'll learn how to find items from one list based on values from another list using Java 8 Streams. How do I sort a list of dictionaries by a value of the dictionary? Java Sorting Java Sorting Learn to use Collections.sort () method to sort a list of objects using some examples. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. C:[a,b,c]. Maybe you can delete one of them. I have created a more general function, that sorts more than two lists based on another one, inspired by @Whatang's answer. Returning a negative number indicates that an element is lesser than another. Then we sort the list. 2) Does listA and listB contain references to the same objects, or just objects that are equivalent with equals()? @Debacle What operations are allowed on the backend over listA? Are there tables of wastage rates for different fruit and veg? More general case (sort list Y by any key instead of the default order), http://scienceoss.com/sort-one-list-by-another-list/, How Intuit democratizes AI development across teams through reusability. What is the shortest way of sorting X using values from Y to get the following output? Zip the two lists together, sort it, then take the parts you want: Also, if you don't mind using numpy arrays (or in fact already are dealing with numpy arrays), here is another nice solution: I found it here: How do I split a list into equally-sized chunks? The second issue is that if listA and listB do contain references to the same objects (which makes the first issue moot, of course), and they contain the same objects (as the OP implied when he said "reordered"), then this whole thing is the same as, And a third major issue is that by the end of this function you're left with some pretty weird side effects. Otherwise, I see a lot of answers here using Collections.sort(), however there is an alternative method which is guaranteed O(2n) runtime, which should theoretically be faster than sort's worst time complexity of O(nlog(n)), at the cost of 2n storage. Created a default comparator on bookings to sort the list. Why do academics stay as adjuncts for years rather than move around? Once you have a list of sorted indices, a simple list comprehension will do the trick: Note that the sorted index list can also be gotten using numpy.argsort(). A Comparator can be passed to Collections.sort () or List.sort () method to allow control over the sort order. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. But it should be: The list is ordered regarding the first element of the pairs, and the comprehension extracts the 'second' element of the pairs. Given parallel lists, how can I sort one while permuting (rearranging) the other in the same way? Making statements based on opinion; back them up with references or personal experience. We can use Collections.reverseOrder () method, which returns a Comparator, for reverse sorting. They reorder the items and want to persist that order (listB), however, due to restrictions I'm unable persist the order on the backend so I have to sort listA after I retrieve it. How do I generate random integers within a specific range in Java? Is there a solution to add special characters from software and how to do it, Minimising the environmental effects of my dyson brain, The difference between the phonemes /p/ and /b/ in Japanese. This can create unstable outputs unless you include the original list indices for the lexicographic ordering to keep duplicates in their original order. The solution here is not to make your class implements Comparator and define a custom comparator class, like. I used java 8 streams to sort lists and put them in ArrayDeques. Is the God of a monotheism necessarily omnipotent? In this case, the key extractor could be the method reference Factory::getPrice (resp. The solution below is simple and does not require any imports. In each iteration, follow the following step . What video game is Charlie playing in Poker Face S01E07? Stop Googling Git commands and actually learn it! HashMaps are a good method for implementing Dictionaries and directories. Originally posted by David O'Meara: Then when you initialise your Comparator, pass in the list used for ordering. Surly Straggler vs. other types of steel frames. How can I pair socks from a pile efficiently? Do I need to loop through them and pass them to the compare method? It throws NullPointerException when comparing null. There are at least two good idioms for this problem. L1-50 first, L2-50 next, then, L2-45, L2-42, L1-40 and L1-30. Whereas, Integer values are directly sorted using Collection.sort(). Just encountered the same problem. Once you have that, define your own comparison function which compares values based on the indexes of list. His title should have been 'How to sort a dictionary?'. Do you know if there is a way to sort multiple lists at once by one sorted index list? Wed like to help. Not the answer you're looking for? In this tutorial we will sort the HashMap according to value. You are using Python 3. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. How to match a specific column position till the end of line? Any suggestions? Why do academics stay as adjuncts for years rather than move around? For example, when appendFirst is false below will be the output. If not then just replace SortedMap indexToObj by SortedMap> indexToObjList. 1. Thanks. You can use this generic comparator to sort list based on the the other list. Thanks. What happens if you have in List1, 50, 40 30 , and in List2 50 45 42? An in-place sort is preferred whenever possible. MathJax reference. I am wondering if there is any easier way to do it. Getting key with maximum value in dictionary? Read our Privacy Policy. All rights reserved. Learn more. A stream represents a sequence of elements and supports different kind of operations that lead to the desired result. This tutorial covered sorting of HashMap according to Value. To sort the String values in the list we use a comparator. Note: the key=operator.itemgetter(1) solves the duplicate issue, zip is not subscriptable you must actually use, If there is more than one matching it gets the first, This does not solve the OPs question. See more examples here. We can sort a list in natural ordering where the list elements must implement Comparable interface. 2023 DigitalOcean, LLC. For more information on how to set\use the key parameter as well as the sorted function in general, take a look at this. Unsubscribe at any time. Sometimes we have to sort a list in Java before processing its elements. Note also, that the SortedDependingList does currently not allow to add an element from listA a second time - in this respect it actually works like a set of elements from listA because this is usually what you want in such a setting. The Collections (Java Doc) class (part of the Java Collection Framework) provides a list of static methods which we can use when working with collections such as list, set and the like. We can use Collections.sort() method to sort a list in the natural ascending order. Using Kolmogorov complexity to measure difficulty of problems? Once you have that, define your own comparison function which compares values based on the indexes of list. zip, sort by the second column, return the first column. It only takes a minute to sign up. The signature of the method is: In the following example, we have used the following methods: The reverseOrder() is a method of Comparator interface which is defined in java.util package. It seems what you want would be to use Comparable instead, but even this isn't a good idea in this case. We've used the respective comparison approaches for the names and ages - comparing names lexicographically using compareTo(), if the age values are the same, and comparing ages regularly via the > operator. Sign up for Infrastructure as a Newsletter. People will search this post looking to sort lists not dictionaries. On the Data tab of the Ribbon, in the Sort & Filter group, click Advanced. Merge two lists in Java and sort them using Object property and another condition, How Intuit democratizes AI development across teams through reusability. zip, sort by the second column, return the first column. Try this. Why is this sentence from The Great Gatsby grammatical? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. This method will also work when both lists are not identical: /** * Sorts list objectsToOrder based on the order of orderedObjects. Note that you can shorten this to a one-liner if you care to: As Wenmin Mu and Jack Peng have pointed out, this assumes that the values in X are all distinct. Linear Algebra - Linear transformation question. Best answer! Solution based on bubble sort (same length required): If the object references should be the same, you can initialize listA new. The order of the elements having the same "key" does not matter. Disconnect between goals and daily tasksIs it me, or the industry? originalList always contains all element from orderedList, but not vice versa. The toList() return the collector which collects all the input elements into a list, in encounter order. To learn more, see our tips on writing great answers. I am a bit confused with FactoryPriceComparator class. (This is a very old answer!). The end result should be list Y being untouched and list X being changed into the expected solution without ever having to create a temp list. Stream.sorted() method : This Stream method is an stateful intermediate operation which sorts elements present in the stream according to natural order @Jack Yes, like what I did in the last example. Create a new list and add first sublist to it. If you try your proposed code, it would give something like this: Person{name=Giant L2, age=100} Person{name=Derp L1, age=50} Person{name=John L2, age=50} Person{name=Menard L1, age=44} Person{name=Lili L1, age=44} Person{name=Lili L2, age=44} Person{name=Menard L2, age=44} Person{name=Bob L1, age=22} Person{name=Alec L1, age=21} Person{name=Herp L1, age=21} Person{name=Alec L2, age=21} Person{name=Herp L2, age=21} Person{name=Alice L1, age=12} Person{name=Little L2, age=5} And it's not what I'm looking for. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. rev2023.3.3.43278. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Sorting a list in Python using the result from sorting another list, How to rearrange one list based on a second list of indices, How to sort a list according to another list? . That's right but the solutions use completely different methods which could be used for different applications. An efficient solution is to first create the mapping from the ID in the ids (your desired IDs order) to the index in that list: And then sort your list of people by the order of their id in this mapping: Note: if a person has an ID that is not present in the ids, they will be placed first in the list. unit tests. Find centralized, trusted content and collaborate around the technologies you use most. Now it actually works. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup, The most efficient way to merge two lists in Java, Java merge sort implementation efficiency. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. It is stable for an ordered stream. Let's save this result into a sortedList: Here we see that the original list stayed unmodified, but we did save the results of the sorting in a new list, allowing us to use both if we need so later on. i.e., it defines how two items in the list should be compared. Finally, we've used a custom Comparator and defined custom sorting logic. Lets look at an example where our value is a custom object. Did you try it with the sample lists. Competitor::getPrice). Then we sort the list. Your compare methods are currently doing: This can be written more concisely with the built-in Double.compare (since Java 7), which also properly handles NaN, -0.0 and 0.0, contrary to your current code: Note that you would have the same implementation for the Comparator. You get paid; we donate to tech nonprofits. If we talk about the working of this method, then the method works on ASCII values. How do you ensure that a red herring doesn't violate Chekhov's gun? We are sorting the names according to firstName, we can also use lastName to sort. On the other hand, a Comparator is a class that is comparing 2 objects of the same type (it does not compare this with another object). Styling contours by colour and by line thickness in QGIS. That's easily managed with an index list: Since the decorate-sort-undecorate approach described by Whatang is a little simpler and works in all cases, it's probably better most of the time.