sort list based on another list java

Here is a solution that increases the time complexity by 2n, but accomplishes what you want. I think that the title of the original question is not accurate. With this method: Sorting a 1000 items list 100 times improves speed 10 times on my Can airtags be tracked from an iMac desktop, with no iPhone? We've sorted Comparable integers and Strings, in ascending and descending order, as well as used a built-in Comparator for custom objects. "Sunday" => 0, , "Saturday" => 6. How to handle a hobby that makes income in US. That way, I can sort any list in the same order as the source list. Did you try it with the sample lists. Note: Any item not in list1 will be ignored since the algorithm will not know what's the sort order to use. Whereas, Integer values are directly sorted using Collection.sort(). It is the method of Java Collections class which belong to a java.lang package. It would be preferable instead to have a method sortCompetitors(), that would sort the list, without leaking it: and remove completely the method getCompetitors(). Let's say we have the following code: Let's sort them by age, first. In java 6 or lower, you need to use. The below example demonstrates the concept of How to sort the List in Java 8 using Lambda Expression. Thanks. "After the incident", I started to be more careful not to trip over things. Basically, this answer is nonsense. Let's say you have a listB list that defines the order in which you want to sort listA. 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. Another alternative, combining several of the answers. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. 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. How can I randomly select an item from a list? good solution! We will use a simple sorting algorithm, Bubble Sort, to sort the elements of a linked list in ascending order below. - the incident has nothing to do with me; can I use this this way? [[name=a, age=age11], [name=a, age=age111], [name=a, age=age1], [name=b, age=age22], [name=b, age=age2], [name=c, age=age33], [name=c, age=age3]]. To learn more, see our tips on writing great answers. The naive implementation that brute force searches listB would not be the best performance-wise, but would be functionally sufficient. The collect() method is used to receive elements from a stream and stored them in a collection. This will provide a quick and easy lookup. What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? Excuse any terrible practices I used while writing this code, though. Using Kolmogorov complexity to measure difficulty of problems? Can Martian regolith be easily melted with microwaves? Here we will learn how to sort a list of Objects in Java. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? We can also pass a Comparator implementation to define the sorting rules. IMO, you need to persist something else. The solution below is simple and does not require any imports. Here is an example of how to sort a list and then make the changes in another list according to the changes exactly made to first array list. rev2023.3.3.43278. Sorting a 10000 items list 100 times improves speed 140 times (265 ms for the whole batch instead of 37 seconds) on my unit tests. To place them last, you can use a nullsLast comparator: I would just use a map with indexes of each name, to simplify the lookup: Then implement a Comparator that sorts by looking up names in indexOfMap: Note that the order of the first elements in the resulting list is not deterministic (because it's just all elements not present in list2, with no further ordering). For example if. For Action, select Filter the list, in-place. 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. Linear regulator thermal information missing in datasheet, How to tell which packages are held back due to phased updates. Another solution that may work depending on your setting is not storing instances in listB but instead indices from listA. My use case is this: user has a list of items initially (listA). Follow Up: struct sockaddr storage initialization by network format-string. - the incident has nothing to do with me; can I use this this way? I like this because I can do multiple lists with one index. The common non-linear data structure known as a tree. A stream represents a sequence of elements and supports different kind of operations that lead to the desired result. You should instead use [x for (y,x) in sorted(zip(Y,X), key=lambda pair: pair[0])]. As you can see that we are using Collections.sort() method to sort the list of Strings. How to make it come last.? 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. The java.Collections.sort () method is also used to sort the linked list, array, queue, and other data structures. 2) Does listA and listB contain references to the same objects, or just objects that are equivalent with equals()? Key Selector Variant. Sometimes we have to sort a list in Java before processing its elements. you can leverage that solution directly in your existing df. When we try to use sort over a zip object. All of the values at the end of the list will be in their order dictated by the list2. Linear regulator thermal information missing in datasheet, Short story taking place on a toroidal planet or moon involving flying, Identify those arcade games from a 1983 Brazilian music video, It is also probably wrong to have your class implements. One way of doing this is looping through listB and adding the items to a temporary list if listA contains them: Not completely clear what you want, but if this is the situation: (This is a very old answer!). Java Sorting Java Sorting Learn to use Collections.sort () method to sort a list of objects using some examples. We first get the String values in a list. Is it possible to create a concave light? Merge two lists in Java and sort them using Object property and another condition, How Intuit democratizes AI development across teams through reusability. You can checkout more examples from our GitHub Repository. It is stable for an ordered stream. This work is licensed under a Creative Commons Attribution-NonCommercial- ShareAlike 4.0 International License. Although I am not entirely sure exactly what the OP is asking for, I couldn't help but come to this conclusion as well. When we try to use sort over a zip object. I think that the title of the original question is not accurate. Both of these variations are instance methods, which require an object of its class to be created before it can be used: This methods returns a stream consisting of the elements of the stream, sorted according to natural order - the ordering provided by the JVM. This is quite inefficient, though, and you should probably create a Map from listA to lookup the positions of the items faster. HashMaps are a good method for implementing Dictionaries and directories. Using this method is fairly simple, so let's take a look at a couple of examples: Here, we make a List instance through the asList() method, providing a few integers and stream() them. 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. Once you have that, define your own comparison function which compares values based on the indexes of list. Note: Any item not in list1 will be ignored since the algorithm will not know what's the sort order to use. 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. You get paid; we donate to tech nonprofits. People will search this post looking to sort lists not dictionaries. The toList() return the collector which collects all the input elements into a list, in encounter order. All rights reserved. 2013-2023 Stack Abuse. In the case of our integers, this means that they're sorted in ascending order. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? L1-50 first, L2-50 next, then, L2-45, L2-42, L1-40 and L1-30. Connect and share knowledge within a single location that is structured and easy to search. This solution is poor when it comes to storage. The size of both list must be same to use this trick. Styling contours by colour and by line thickness in QGIS. This is an old question but some of the answers I see posted don't actually work because zip is not scriptable. 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. 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Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. I need to sort the list of factories based on price of their items and also sort list of other items from competitors for each factory. Does Counterspell prevent from any further spells being cast on a given turn? So we pass User::getCreatedOn to sort by the createdOn field. We can sort a list in natural ordering where the list elements must implement Comparable interface. If they are already numpy arrays, then it's simply. How do I sort a list of dictionaries by a value of the dictionary? So basically, I have 2 ArrayLists (listA and listB). then the question should be 'How to sort a dictionary? It returns a stream sorted according to the natural order. The answer of riza might be useful when plotting data, since zip(*sorted(zip(X, Y), key=lambda pair: pair[0])) returns both the sorted X and Y sorted with values of X. You can do list1.addAll(list2) and then sort list1 which now contains both lists. Why is "1000000000000000 in range(1000000000000001)" so fast in Python 3? Edit: Fixed this line return this.left.compareTo(o.left);. test bed for array based list implementation, Reading rows based on column value in POI. 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. Using a For-Each Loop This comparator sorts the list of values alphabetically. Copyright 2011-2021 www.javatpoint.com. If values in the HashMap are of type Integer, the code will be as follows : Here HashMap values are sorted according to Integer values. We can use Collections.sort() method to sort a list in the natural ascending order. I mean swapItems(), removeItem(), addItem(), setItem() ?? 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. Making statements based on opinion; back them up with references or personal experience. All rights reserved. DigitalOcean makes it simple to launch in the cloud and scale up as you grow whether youre running one virtual machine or ten thousand. The solution below is the most efficient in this case: Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Originally posted by David O'Meara: Then when you initialise your Comparator, pass in the list used for ordering. The second one is easier and faster if you're not using Pandas in your program. - the incident has nothing to do with me; can I use this this way? If you're using Java 8, you can even get rid of the above FactoryPriceComparator and use the built-in Comparator.comparingDouble(keyExtractor), which creates a comparator comparing the double values returned by the key extractor. Better example data would be quite helpful, too. If you have 2 lists of identical number of items and where every item in list 1 is related to list 2 in the same order (e.g a = 0 , b = 1, etc.) Connect and share knowledge within a single location that is structured and easy to search. Note: The LinkedList elements must implement the Comparable interface for this method to work. You can use this generic comparator to sort list based on the the other list. 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. The Comparator.comparing static function accepts a sort key Function and returns a Comparator for the type that contains the sort key: To see this in action, we'll use the name field in Employee as the sort key, and pass its method reference as an argument of type Function. Whats the grammar of "For those whose stories they are"? Its likely the second set is a subset of the first. What video game is Charlie playing in Poker Face S01E07?