For MutableList (which has mutating functions, in contrast with List), there is a plusAssign operator implementation, that can be used as follows: A different approach by using spread operator. You could do this by, for example, slicing the list around the element you want to change, and building your final list from those parts: This way you get to take advantage of any efficiency from the underlying list copy methods, versus map which has to "transform" each item even if it ends up passing through the original. 1 The simpler way is finding the index of the element you want to replace and the set the new value for it as follows: var list: ArrayList<String> = arrayListOf ("one", "two", "three") int index = list.indexOf ("two"); list.set (index, "four"); forEach. Ole Miss head coach Lane Kiffin. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing. The index of an ArrayList is zero-based. println(numbers) val numbers = mutableListOf(1, 2, 3, 4, 3) //sampleEnd //sampleEnd println(numbers.joinToString(separator = " | ", prefix = "start: ", postfix = ": end")) Did the US government claim that it has the right to control "cognitive infrastructure", i.e. A mutable list allows us to append and modify elements. Does a Wand of Secrets still point to a revealed secret or sprung trap? To apply a transformation that additionally uses the element index as an argument, use mapIndexed(). In programming, lists are also very useful. numbers.addAll(2, listOf("three", "four")) numbers.reverse() println(numbers.associateBy { it.first().uppercaseChar() }) How to replace index value in mutableListOf? What is the best way to replace element in immutable list? In any lists, you can find the position of an element using the functions indexOf() and lastIndexOf(). Maybe in some case would be simpler than using + sign or mutableListOf. This article explores different ways to replace values in a list in Kotlin. val colors = listOf("red", "brown", "grey") In the Kotlin standard library, this is done by the zip() extension function. What is the best way to "replace" an element of an immutable list? //sampleEnd Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. println("Sort into ascending: $numbers") In any lists, you can find the position of an element using the functions indexOf () and lastIndexOf (). The list must be sorted in ascending order according to this Comparator. Asking for help, clarification, or responding to other answers. Not the answer you're looking for? println(numbers.mapIndexedNotNull { idx, value -> if (idx == 0) null else value * idx }) Does attorney client privilege apply when lawyers are fraudulent about credentials? println(numbers.getOrElse(5, {it})) // 5 Then, we simply verify the condition and use the index number to directly set the value in that position: In Kotlin, its possible to extend the capabilities of a class without inheriting or creating a decorator class. Preserving backwards compatibility when adding new keywords. Well create an extension method on the MutableList class that allows us to apply an operation on every element of the list. Thanks for contributing an answer to Stack Overflow! //sampleStart First split the string to a list of its words and then map each word if it exists in list a to the corresponding word in list b. //sampleEnd }, fun main() { But as always, it's best to benchmark to see how well these approaches actually perform! val productList = listOf( In this article, well go through several ways that we can use to efficiently update lists in place. The resulting string will start with the prefix and end with the postfix. Modifying point density depending on Z position when using distribute points on faces. Product("DotTrace", 129.0), We can simply compare the value returned by the mutator function with the current element: This function can be easily generalized to work with a list of any type: We can also use an extension method with an Array class: In this article, weve seen how to update a list as we iterate over it by applying different methods. Thus, if an element of the original collection changes, it also changes in the previously created sublists and vice versa. val numbers = listOf("one", "two", "three", "four") The standard solution to replace values in a list is using the replaceAll() function. In Kotlin, lists are either mutable or immutable. Is it legal to cross an internal Schengen border without passport for a day visit. Using a for loop, we iterate from 0 to N 1, where N is the number of elements in the list. Another way of modifying the elements of a list in-place is by setting the value for a specific index. Can Loss by Checkmate be Avoided by Invoking the 50-Move Rule Immediately After the 100th Half-Move? We are sorry that this post was not useful for you! Techniques for Spring Developers" webinar and learn how to: Add new functionality to existing classes with Kotlin extension And then theres also the possibility to convert your list into a Sequence: this way it will be lazily evaluated; every replacement you add with .map will create a new Sequence that refers to the old one plus your new mapping, and none of it will be evaluated until you run an operation that actually has to read the whole thing, like toList(). val productList = listOf( The separator will come after each element except the last. //sampleStart 588), Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned. 1. Is a thumbs-up emoji considered as legally binding agreement in the United States? Kotlin. No votes so far! How can I change an object field in a list and return the list with the changed object? If Instagram . Syntax: ArrayList<Integer> gfg=new ArrayList<> (); ArrayList<Integer> gfg2=gfg; Below is the implementation of the above problem statement. In addition to common operations for Retrieving Collection Parts, lists provide the subList() function that returns a view of the specified elements range as a list. //sampleStart println(listString) If so, we return 0, otherwise, we return the element without changes. If you can guarantee that id is unique, you can do it like this instead: firstOrNull returns the first element matching the condition, or null if there is none. To treat the replacement string Conclusions from title-drafting and question-content assistance experiments Update (or Replace) item(s) in immutable collection in Scala. rev2023.7.13.43531. The in-place sorting functions have similar names to the functions that apply to read-only lists, but without the ed/d suffix: sort* instead of sorted* in the names of all sorting functions: sort(), sortDescending(), sortBy(), and so on. Were creating a new method called mapInPlace for Int elements in the MutableList class that will be available within the context of our application. fun main() { Find centralized, trusted content and collaborate around the technologies you use most. I wanted a Scala-like with for and yield. The run enclosure in your code is not being used for anything so you might as well remove it. println(numbers.getOrNull(5)) // null Both functions use the transformations that take a map entry as an argument, so you can operate both its key and value. //sampleStart //sampleStart Example : fun main () { var x = mutableListOf ("Mohan", "Kriti", "Salim") x [1] = "Paul" println (x) } Output : [Person(name=James, age=18, cat=Adult), Person(name=Mary, age=20, cat=Adult), Person(name=Jennifer, age=25, cat=Adult)]. All indices of elements that come after the element being removed will decrease by one. Why speed of light is considered to be the fastest? indexOfLast() returns the index of the last element matching the predicate or -1 if there are no such elements. //sampleEnd val numbers = listOf("one", "two", "three", "four") numbers.add(1, "two") The simpler way is finding the index of the element you want to replace and the set the new value for it as follows: Thanks for contributing an answer to Stack Overflow! All the methods in this interface support read-only access to the list. println(numbers.joinToString { "Element: ${it.uppercase()}"}) }, fun main() { It is O(1) to replace an item and it almost doesn't use any additional memory. Lists are one of the most common data structures used by developers in their day-to-day work lives. Binary search with comparison function lets you find elements without providing explicit search values. Sum of a range of a sum of a range of a sum of a range of a sum of a range of a sum of. To what uses would adamant, a rare stone-like material that is literally unbreakable, be put? println(numbers.joinToString()) If there are no such elements, both functions return -1. Optimize the speed of a safe prime finder in C. A player falls asleep during the game and his friend wakes him -- illegal? if (nameParts.size == 2) { The new app, Threads, was unveiled on Wednesday as a companion to Instagram, the popular photo-sharing network that Mr. Zuckerberg's company, Meta, bought more than a decade ago. println(numbers.joinToString(limit = 10, truncated = "<>")) To replace an element in Java ArrayList, set () method of java.util. zip () Pair List . }, import kotlin.math.sign Can my US citizen child get into Japan, if passport expires in less than six months? Are packaged masalas to be used in combination with or instead of other spices? To learn more, see our tips on writing great answers. The basic mapping function is map(). Note that associate() produces short-living Pair objects which may affect the performance. To build a custom string representation, you can specify its parameters in function arguments separator, prefix, and postfix. println(productList.binarySearch { priceComparison(it, 99.0) }) How to replace last character in String when it is in an Array, Replace element in ArrayList of objects [Kotlin], Unable to replace string inside a String in Kotlin, How to replace string characters that are not in a reference list in kotlin. //sampleStart println("Sort into descending: $numbers") To learn more, see our tips on writing great answers. Thanks for contributing an answer to Stack Overflow! }, fun main() { = null) { override fun toString(): String { return if (next != null) { "$value -> $ {next.toString ()}" } else { "$value" } } } Navigate to the Main.kt file and add the following inside main (): //sampleEnd By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. println(colors.zip(twoAnimals)) //sampleEnd xxxxxxxxxx val inputString0 = "Mississippi" getOrNull() returns null as the default value. This is fairly easy to do in Kotlin: . The first function is flatten(). I guess you could change your first approach to manually iterate, but that doesn't really change the behavior, and it would be more verbose. //sampleStart //sampleEnd functions. Kotlin - replace item in a map. println(numberSets.flatten()) Kotlin Mutable List is a collection of elements which can support modifications to the List. println(numbers) Another way to build maps in which both keys and values are somehow produced from collection elements is the function associate(). Considering what you actually need to do here (get a copy of the list and change (up to) one thing) the last approach seems like the best fit! To only modify the first matching object, use the find() function. val listString = StringBuffer("The list of numbers: ") Equivariant perverse sheaves and orbit stratification, Tikz Calendar - how to pass argument with '\def'. Product("ReSharper", 149.0)) Its contents might be getting changed internally in the class that owns the list. //sampleEnd with the result of the given function transform that takes MatchResult and returns a string to be used as a As long as you don't mutate it while it is in use by that other class, it would be OK. Another thing you could try is, as apparently each item has an id field that you are using to identify the item, to create a map from it, perform all your replacements on that map, and convert it back into a list. Another solution: if the list is truly immutable and not only read-only; or if its contents could change and you would like to see these changes in the resulting list, then you can also wrap the original list into another one. It replaces each element of the list with the result of applying the specified operator to it. (The compiler version: java 8). Not that I know of. val numbers = (0..13).toList() numbers.sortBy { it.length } When called on a collection or an array with another collection (or array) as an argument, zip() returns the List of Pair objects. Someone opened a feature request for a dedicated function. println("Sort into ascending by length: $numbers") Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, this is the most descriptive answer and thank you very much @moira, parse and replace a list of object in kotlin, Exploring the infrastructure and code behind modern edge functions, Jamstack is evolving toward a composable web (Ep. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Can I do a Performance during combat? List Mutable ( ) Immutable () . safe call operator returns null if the left operand is null, otherwise, it calls the method. zip() can also be called in the infix form a zip b. The first one iterates the list up to 2 times, but the second iteration breaks early once it finds the item. Can Loss by Checkmate be Avoided by Invoking the 50-Move Rule Immediately After the 100th Half-Move? expressive code. with the specified newValue string. Kotlin noob here, I'm trying to update the element in listFirst by comparing some attribute (say, topicId) of the elements from the listSecond, both list contains the same type of element. println(productList.binarySearch(Product("AppCode", 99.0), compareBy { it.price }.thenBy { it.name })) }, fun main() { To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 22 The Kotlin lists have the plus operator overloaded in kotlin-stdlib, so you can add an item to a list: val values = listOf (1, 2, 3, 4, 5, 6) return values + 7 There's also an overload that adds another list: val values = listOf (1, 2, 3, 4, 5, 6) return listOf (-1, 0) + values + listOf (7, 8) What is the "salvation ready to be revealed in the last time"? There is one more way to search elements in lists binary search. 0. The second one iterates the list a single time, but it does have to do the ID comparison for each item in the list. StringContainer(listOf("four", "five", "six")), Connect and share knowledge within a single location that is structured and easy to search. First, you're missing comma after properties in your data classes, so it should be: As for second problem, there're probably number of ways to do that, but I've only corrected your idea: Instead of assigning values to variables, you can name parameter for forEach and use it in rest of the loop. The following example shows sorting functions for mutable lists: fun main() { A list is a generic ordered collection of elements. If two elements are equal, only the last one remains in the map. To conditionally modify a field in a list of objects, we can filter the list using the filter() function and perform the given action on each element of the filtered list: Output: And I have several ways to update list: The second option looks more concise and I like it more. That would be kind of a fragile design, but it's possible. The method will receive a function as a parameter, and well apply this function to every element in the list. Which superhero wears red, white, and blue, and works as a furniture mover? 1. how to update a list by an other list of the same type on kotlin. numbers.sortWith(compareBy { it.length }.thenBy { it }) This article explores different ways to conditionally remove elements from a mutable list in Kotlin. rev2023.7.13.43531. val numbers = listOf("one", "two", "three", "four") Why does this demonstration of a GLM have a confident fit so far from the truth? Find centralized, trusted content and collaborate around the technologies you use most. What is the purpose of putting the last scene first? To learn more, see our tips on writing great answers. val numbers = mutableListOf("one", "five", "three") Replace occurence in a String in Kotlin Ask Question Asked 4 years, 2 months ago Modified 2 years, 7 months ago Viewed 2k times 0 I have two list of Strings. println(numbers.lastIndexOf(2)) By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. println("Reverse: $numbers") thanks for pointing this out! numbers.shuffle() We can also use the Kotlin keyword it to access the element inside the brackets: A possible improvement for the mapInPlace function is to check if the element has really changed before inserting it. We can add elements to or remove elements from this Mutable List. Join the >> "Advanced Kotlin //sampleStart In this tutorial we will get acquainted with templates and filters, modify a predefined template, and then create a code inspection based on it. 588), Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned. Now I want to replace every occurence of a word in the first list at index i with a word in the second list at index i of a sentence. Which spells benefit most from upcasting? Can Loss by Checkmate be Avoided by Invoking the 50-Move Rule Immediately After the 100th Half-Move? //sampleStart 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. val numbers = (1..100).toList() Output: the advanced Kotlin techniques that are available to you as a with the given replacement. And slicing takes 2-3x longer than just a straight mutable copy and update. How to create a list from specific indexes in list of lists in Kotlin? val numbers = listOf("one", "two", "three", "four") This method changes the value of the last element retrieved through the next() method. how to remove an element at a specified location from a list in Kotlin? Your last code block, corrected, would be: This loops through each update, filters tools for tools with the right ID, and sets the name of each of these tools. fun main() { I came up with the following ugly solution: val list = listOf (1, 2, 3) val updatedList = listOf (99, * (list.subList (1, list.size).toTypedArray ())) However, despite being a bit noisy it would get even worse if you want to replace an element in the middle of the list. numbers.sortByDescending { it.last() } Asking for help, clarification, or responding to other answers. 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 list must be sorted in the ascending order according to the provided function; in other words, the return values of comparison must grow from one list element to the next one. As usual, code snippets can be found over on GitHub. literally escape it with the kotlin.text.Regex.Companion.escapeReplacement method. The high level overview of all the articles on the site. How do I replace multiple characters in a String? println(numbersMap.mapKeys { it.key.uppercase() }) Additionally, your constructor parameters to the data class are normal parameters, and as such, need commas between them! Sometimes, it might be extremely necessary to efficiently work with lists, especially when they contain a lot of elements. Can Loss by Checkmate be Avoided by Invoking the 50-Move Rule Immediately After the 100th Half-Move? By using this site, you agree to the use of cookies, our policies, copyright terms and other conditions. Which superhero wears red, white, and blue, and works as a furniture mover? This would change it from O(n^2) to O(n). There are situations where you might want to use a MutableList for performance reasons and pass it to other functions that only expect a read-only List. Replace element in ArrayList of objects [Kotlin]. Another typical approach is to kinda go half-and-half, copying the parts you need, and inserting the bits you want to change. Does it cost an action? There is also a pair of functions that take a predicate and search for elements matching it: indexOfFirst() returns the index of the first element matching the predicate or -1 if there are no such elements. Map Such operations use the index to access elements to broaden the list modification capabilities. We can iterate over a collection using an iterator. Connect and share knowledge within a single location that is structured and easy to search. There are two other functions that help you avoid such exceptions: getOrElse() lets you provide the function for calculating the default value to return if the index isn't present in the collection. What is the purpose of putting the last scene first? To apply a given transformation to keys, use mapKeys(); in turn, mapValues() transforms values. //sampleStart Lets see an example of a mutator function: As we can see, for every element in the list, we verify if its an even number. I had the following code but it looks ugly to me. Kotlin listOf The listOf method creates a new read-only list in Kotlin. //sampleEnd Question from IQ test involving patterns of white, yellow, red, and grey squares. println(numberPairs.unzip()) //sampleEnd Zipping transformation is building pairs from elements with the same positions in both collections. numbers.joinTo(listString) //sampleEnd, fun main() { val numbers = mutableListOf("one", "two", "three", "four") And I need to replace "two" with "four", so I need to delete it and replace at the same place with "four" but i don't know where is "two" is located. So, having a list sorted ascending according to this order, we use binarySearch() to find the index of the specified Product. fill() simply replaces all the collection elements with the specified value. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. val nameParts = fullName.split(" ") Is it legal to cross an internal Schengen border without passport for a day visit. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. In this Kotlin Tutorial - Kotlin Replace String, we have learnt how to replace a old value with a new value in a string. I would like to return another list with a new element. println(numbers) in the predicate passed to find, which should only return a Boolean value to filter elements, and should probably not have any side effects, those should be done later with a call to i.e. Why don't the first two laws of thermodynamics contradict each other? In what ways was the Windows NT POSIX implementation unsuited to real use? Returns a new string obtained by replacing all occurrences of the oldValue substring in this string }, data class StringContainer(val values: List) We have also dealt with ignoring case while replacing the string with Kotlin Examples. }, fun main() { fun <T, R> Iterable<T>.runningFoldIndexed(. Is every finite poset a subset of a finite complemented distributive lattice? To search an element in a sorted list, call the binarySearch() function passing the value as an argument. 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. //sampleStart On the other hand, we cant modify an immutable list after we have created it. Product("AppCode", 99.0), Thus, associate() should be used when the performance isn't critical or it's more preferable than other options. Modifying a list in-place means updating its values at the same time that were looping over the list. Making statements based on opinion; back them up with references or personal experience. Why do disk brakes generate "more stopping power" than rim brakes? Connect and share knowledge within a single location that is structured and easy to search. val numbers = mutableListOf("one", "five", "six") Is it possible to play in D-tuning (guitar) on keyboards? A "simpler" description of the automorphism group of the Lamplighter group, IQ question involving patterns of lines joined together. Here's a playground example - definitely not the best place to do benchmarking, but it can be instructive as a general ballpark if you run things a few times: Broadly speaking, mapping takes 60-100% more time than the slice-and-combine approach. Not the answer you're looking for? All elements that come after the position shift to the right. [Person(name=James, age=18, cat=null), Person(name=Mary, age=21, cat=null), Person(name=Jennifer, age=25, cat=null)]. Immutable get . println(numbers.binarySearch("z")) // -5 Does a Wand of Secrets still point to a revealed secret or sprung trap? }, fun main() { Why is Singapore placed so low in the democracy index? Is it okay to change the key signature in the middle of a bar? "As much as" / "autant (de) que": amount or number of times? Iterate through array in Kotlin to replace elements. Enter your email address to subscribe to new posts. For example: To an outside class, this List is read-only, but not immutable. }, fun main() { Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, This creates and returns a copy of the list. } If n distinct objects are distributed randomly into n distinct boxes, what is the probability that exactly two boxes are empty? Thank you for answer. If the transformation produces null on certain elements, you can filter out the nulls from the result collection by calling the mapNotNull() function instead of map(), or mapIndexedNotNull() instead of mapIndexed(). Side note: "immutable" is not really the right term for a List. How do I store ready-to-eat salad better? //sampleEnd Conclusions from title-drafting and question-content assistance experiments Update objects in list from objects in another list in kotlin. The standard Kotlin library provides many beneficial functions to filter a List. The predicates are simple lambda expressions. Is tabbing the best/only accessibility solution on a data heavy map UI? To add elements to a specific position in a list, use add() and addAll() providing the position for element insertion as an additional argument. Is a thumbs-up emoji considered as legally binding agreement in the United States? The mutable list is invariant in its element type. //sampleStart Sometimes, it might be extremely necessary to efficiently work with lists, especially when they contain a lot of elements. associateBy() can also be called with a value transformation function. joinToString() builds a single String from the collection elements based on the provided arguments. I want the sentence "I am an amateur" To what uses would adamant, a rare stone-like material that is literally unbreakable, be put? Thanks for contributing an answer to Stack Overflow! those should be done later with a call to i.e. Could a pre-industrial society make a heavy load neutrally buoyant? If such an element exists, the function returns its index; otherwise, it returns (-insertionPoint - 1) where insertionPoint is the index where this element should be inserted so that the list remains sorted. . void, nothing), using the safe call operator simply does nothing if the left operand is null. Kotlin way to update elements in one list from elements in another list? And we want to replace the name 'Kriti' with a new name 'Paul'. Here we call a transform function on an element first, and then build a pair from the properties of that function's result. When you have a List of Pairs, you can do the reverse transformation unzipping that builds two lists from these pairs: The first list contains the first elements of each Pair in the original list. In addition to the collection modification operations described in Collection write operations, mutable lists support specific write operations. println(numbers.indexOfLast { it % 2 == 1}) Before you begin It's common to make lists for all sorts of situations in your everyday life such as a list of things to do, a list of guests for an event, a wish list, or a grocery list. any idea ? kotlin.text.Regex.Companion.escapeReplacement. val twoAnimals = listOf("fox", "bear") 1.0 fun String.replace( oldValue: String, newValue: String, ignoreCase: Boolean = false ): String (Common source) (JVM source) (JS source) (Native source) Returns a new string obtained by replacing all occurrences of the oldValue substring in this string with the specified newValue string. Parameters E - the type of elements contained in the list. }, fun main() { Is there an equation similar to square root, but faster for a computer to compute? //sampleStart You can partially optimize this by detecting you invoke getItem() on your specific implementation, but even better, you can use already existing libraries that does this. Making statements based on opinion; back them up with references or personal experience. It takes a function that returns a key based on an element's value. //sampleStart The function returns a single List of all the elements of the nested collections. What is the easiest way to change element in the list Kotlin?
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kotlin replace list with another list
kotlin replace list with another list
