sort list based on another list java

Assuming that the larger list contains all values in the smaller list, it can be done. 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.) 2023 ITCodar.com. 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. 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. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. As you can see that we are using Collections.sort() method to sort the list of Strings. See more examples here. 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: We can use this by creating a list of Integers and sort these using the Collections.sort(). sorting the list based on another list (Java in General forum at Coderanch) A:[c,b,a] 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. Java 8 - How to sort ArrayList using Stream API - BenchResources.Net It throws NullPointerException when comparing null. 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. I see where you are going with it, but you need to rethink what you were going for and edit this answer. His title should have been 'How to sort a dictionary?'. Returning a negative number indicates that an element is lesser than another. How do you get out of a corner when plotting yourself into a corner, Trying to understand how to get this basic Fourier Series. It returns a comparator that imposes reverse of the natural ordering. For example, explain why your solution is better, explain the reasoning behind your solution, etc. More elegant code or using some built in Java class? If they are already numpy arrays, then it's simply. How to make it come last.? You can setup history as a HashMap or separate class to make this easier. Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. will be problematic in the future. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. MathJax reference. The common non-linear data structure known as a tree. All rights reserved. This is quite inefficient, though, and you should probably create a Map from listA to lookup the positions of the items faster. This work is licensed under a Creative Commons Attribution-NonCommercial- ShareAlike 4.0 International License. We can also pass a Comparator implementation to define the sorting rules. His title should have been 'How to sort a dictionary?'. The returned comparable is serializable. 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. Application of Binary Tree. Sort a List of objects by multiple attributes in Java 2013-2023 Stack Abuse. I can resort to the use of for constructs but I am curious if there is a shorter way. The solution assumes that all the objects in the list to sort have distinct keys. 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? This tutorial covered sorting of HashMap according to Value. super T> comparator), Defining a Custom Comparator with Stream.sorted(). 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. Mail us on [emailprotected], to get more information about given services. In this quick tutorial, we'll learn how to find items from one list based on values from another list using Java 8 Streams. Sorting values of a dictionary based on a list. It would be helpful if you would provide an example of your expected input and output. It returns a stream sorted according to the natural order. L1-50 first, L2-50 next, then, L2-45, L2-42, L1-40 and L1-30. There are plenty of ways to achieve this. The order of the elements having the same "key" does not matter. To learn more, see our tips on writing great answers. We can now eliminate the anonymous inner class and achieve the same result with simple, functional semantics using lambdas: (Employee e1, Employee e2) -> e1.getName ().compareTo (e2.getName ()); We can test it as below: 2. How to use Java Lambda expression for sorting a List using comparator Java Collections sort() - HowToDoInJava The solution below is the most efficient in this case: Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Sort a List of Integers 5 1 List<Integer> numbers = Arrays.asList(6, 2, 1, 4, 9); 2 System.out.println(numbers); 3 4 numbers.sort(Comparator.naturalOrder()); 5 System.out.println(numbers);. C:[a,b,c]. 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. You weren't kidding. It is the method of Java Collections class which belong to a java.lang package. You are using Python 3. You can implement a custom Comparator to sort a list by multiple attributes. My solution: The time complexity is O(N * Log(N)). "After the incident", I started to be more careful not to trip over things. How to Sort a List in Java | DigitalOcean O(n) look up happening roughly O(nlogn) times? What I am doing require to sort collection of factories and loop through all factories and sort collection of their competitors. The most obvious solution to me is to use the key keyword arg. not if you call the sort after merging the list as suggested here. Here is Whatangs answer if you want to get both sorted lists (python3). How to use Slater Type Orbitals as a basis functions in matrix method correctly? Minimising the environmental effects of my dyson brain. May be not the full listB, but something. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Using Kolmogorov complexity to measure difficulty of problems? I think most of the solutions above will not work if the 2 lists are of different sizes or contain different items. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. For bigger arrays / vectors, this solution with numpy is beneficial! rev2023.3.3.43278. 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. Is it possible to rotate a window 90 degrees if it has the same length and width? With this method: Sorting a 1000 items list 100 times improves speed 10 times on my No new elements. We first get the String values in a list. Key and Value can be of different types (eg - String, Integer). If we sort the Users, and two of them have the same age, they're now sorted by the order of insertion, not their natural order, based on their names. If the age of the users is the same, the first one that was added to the list will be the first in the sorted order. 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. To sort the String values in the list we use a comparator. In the case of our integers, this means that they're sorted in ascending order. Now it produces an iterable object. In Java there are set of classes which can be useful to sort lists or arrays. My question is how to call compare method of factoryPriceComparator to sort factories? Does this assume that the lists are of same size? How To Sort the List in Java 8 - Making Java easy to learn Once you have that, define your own comparison function which compares values based on the indexes of list. The solution below is simple and does not require any imports. It is defined in Stream interface which is present in java.util package. Wed like to help. Something like this? MathJax reference. 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. Originally posted by David O'Meara: Then when you initialise your Comparator, pass in the list used for ordering. rev2023.3.3.43278. We first get the String values in a list. Now it actually works. Sorting values of a dictionary based on a list. Linear regulator thermal information missing in datasheet, How to tell which packages are held back due to phased updates. I think most of the solutions above will not work if the 2 lists are of different sizes or contain different items. 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. 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. . Sorry, that was my typo. How can I randomly select an item from a list? 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. i.e., it defines how two items in the list should be compared. Find centralized, trusted content and collaborate around the technologies you use most. Find centralized, trusted content and collaborate around the technologies you use most. What am I doing wrong here in the PlotLegends specification? @RichieV I recommend using Quicksort or an in-place merge sort implementation. This will provide a quick and easy lookup. @Jack Yes, like what I did in the last example. If not then just replace SortedMap indexToObj by SortedMap> indexToObjList. Sort an array of strings based on the given order I am also wandering if there is a better way to do that. The best answers are voted up and rise to the top, Not the answer you're looking for? Now it produces an iterable object. If you have any suggestions for improvements, please let us know by clicking the report an issue button at the bottom of the tutorial. 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. What video game is Charlie playing in Poker Face S01E07? How do I read / convert an InputStream into a String in Java? Other answers didn't bother to import operator and provide more info about this module and its benefits here. We've sorted Comparable integers and Strings, in ascending and descending order, as well as used a built-in Comparator for custom objects. 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. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? I did a static include of. The toList() return the collector which collects all the input elements into a list, in encounter order. Once we have the list of values in a sorted manner, we build the HashMap again based on this new list. 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. 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. I have created a more general function, that sorts more than two lists based on another one, inspired by @Whatang's answer. How is an ETF fee calculated in a trade that ends in less than a year? The method returns a comparator that imposes the reverse of the natural ordering. The java.Collections.sort () method sorts the list elements by comparing the ASCII values of the elements. We can sort a list in natural ordering where the list elements must implement Comparable interface. Not the answer you're looking for? 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. @Debacle What operations are allowed on the backend over listA? Sorting list according to corresponding values from a parallel list [duplicate]. In java 6 or lower, you need to use. Each factory has an item of its own and a list of other items from competitors. They're functional in nature, and it's worth noting that operations on a stream produce a result, but do not modify its source. Why is "1000000000000000 in range(1000000000000001)" so fast in Python 3? 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. Thanks. Merge two lists in Java and sort them using Object property and another condition, How Intuit democratizes AI development across teams through reusability. Take a look at this solution, may be this is what you are trying to achieve: O U T P U T @RichieV I recommend using Quicksort or an in-place merge sort implementation. In this case, the key extractor could be the method reference Factory::getPrice (resp. Get tutorials, guides, and dev jobs in your inbox. In case of Strings, they're sorted lexicographically: If we wanted the newly sorted list saved, the same procedure as with the integers applies here: Check out our hands-on, practical guide to learning Git, with best-practices, industry-accepted standards, and included cheat sheet. The Comparator.comparing () method accepts a method reference which serves as the basis of the comparison. 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. All rights reserved. Speed improvement on JB Nizet's answer (from the suggestion he made himself). As for won't work..that's right because he posted the wrong question in the title when he talked about lists. 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. Sometimes we have to sort a list in Java before processing its elements. 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? You posted your solution two times. Collections class sort() method is used to sort a list in Java. 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? Python. Find centralized, trusted content and collaborate around the technologies you use most. DigitalOcean makes it simple to launch in the cloud and scale up as you grow whether youre running one virtual machine or ten thousand. Are there tables of wastage rates for different fruit and veg? 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? DigitalOcean makes it simple to launch in the cloud and scale up as you grow whether youre running one virtual machine or ten thousand. Starting with the example input you provided: This is also known as the Schwartzian_transform after R. Schwartz who popularized this pattern in Perl in the 90s: Note that in this case Y and X are sorted and compared lexicographically. - Hatefiend HashMaps are a good method for implementing Dictionaries and directories. Also easy extendable for similar problems! That way, I can sort any list in the same order as the source list. Then we sort the list. @Debacle: Please clarify two things: 1) Is there a 1:1 correspondance between listA and listB? Surly Straggler vs. other types of steel frames. Is there a single-word adjective for "having exceptionally strong moral principles"? So in a nutshell, we can sort a list by simply calling: java.util.Collections.sort(the list) as shown in the following example: The above class creates a list of four integers and, using the collection sort method, sorts this list (in one line of code) without us having to worry about the sorting algorithm. 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. I want to sort listA based on listB. Sorting for String values differs from Integer values. Whats the grammar of "For those whose stories they are"? zip, sort by the second column, return the first column. Else, run a loop till the last node (i.e. May be just the indexes of the items that the user changed. 3.1. Thanks for contributing an answer to Code Review Stack Exchange! Sorting a list based on another list's values - Java 16,973 Solution 1 Get rid of the two Lists. We can use the following methods to sort the list: Using stream.sorted () method Using Comparator.reverseOrder () method Using Comparator.naturalOrder () method Using Collections.reverseOrder () method Using Collections.sort () method Java Stream interface Java Stream interface provides two methods for sorting the list: sorted () method Working on improving health and education, reducing inequality, and spurring economic growth? If so, how close was it? Warning: If you run it with empty lists it crashes. How can I randomly select an item from a list? All of the values at the end of the list will be in their order dictated by the list2. This can create unstable outputs unless you include the original list indices for the lexicographic ordering to keep duplicates in their original order. In this tutorial, we'll compare some filtering implementations and discuss their advantages and drawbacks. Another alternative, combining several of the answers. I am a bit confused with FactoryPriceComparator class. Sorting a List of Integers with Stream.sorted () Found within the Stream interface, the sorted () method has two overloaded variations that we'll be looking into. Theoretically Correct vs Practical Notation. If changes are possible, you would need to somehow listen for changes to the original list and update the indices inside the custom list. Has 90% of ice around Antarctica disappeared in less than a decade? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. good solution! In this quick tutorial, we'll learn how to find items from one list based on values from another list using Java 8 Streams. Is the God of a monotheism necessarily omnipotent? When we try to use sort over a zip object. Can I tell police to wait and call a lawyer when served with a search warrant? How can this new ban on drag possibly be considered constitutional? If they are already numpy arrays, then it's simply. "After the incident", I started to be more careful not to trip over things. Warning: If you run it with empty lists it crashes. The preferred way to add something to SortedDependingList is by already knowing the index of an element and adding it by calling sortedList.addByIndex(index); If the two lists are guaranteed to contain the same elements, just in a different order, you can use List listA = new ArrayList<>(listB) and this will be O(n) time complexity. Given an array of strings words [] and the sequential order of alphabets, our task is to sort the array according to the order given. Java LinkedList Sort Example - Java Code Examples Making statements based on opinion; back them up with references or personal experience. Learn more about Stack Overflow the company, and our products. rev2023.3.3.43278. good solution! What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? Did you try it with the sample lists. This comparator sorts the list of values alphabetically. As each pair of strings are passed in for comparison, convert them into ints using originalList.indexOf, except that if the index is -1, change the index to originalList.size () Compare the two ints. A example will show this. Let's say we have the following code: Let's sort them by age, first. How to remove an element from a list by index, Sorting an array of objects by property values, String formatting: % vs. .format vs. f-string literal. 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: Its likely the second set is a subset of the first. Disconnect between goals and daily tasksIs it me, or the industry? Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? An in-place sort is preferred whenever possible. @Hatefiend interesting, could you point to a reference on how to achieve that? 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. We can use Collections.reverseOrder () method, which returns a Comparator, for reverse sorting. Here is my complete code to achieve this result: But, is there another way to do it? Sorting a Java list collection using Lambda expression Since Java 8 with Lambda expressions support, we can write a comparator in a more concise way as follows: 1 Comparator<Book> descPriceComp = (Book b1, Book b2) -> (int) (b2.getPrice () - b1.getPrice ()); 2023 DigitalOcean, LLC. I am also wandering if there is a better way to do that. Does Counterspell prevent from any further spells being cast on a given turn? The code below is general purpose for a scenario where listA is a list of Objects since you did not indicate a particular type. In our case, we're using the getAge() method as the sorting key. When we try to use sort over a zip object. Since Comparator is a functional interface, we can use lambda expressions to write its implementation in a single line. 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. "Sunday" => 0, , "Saturday" => 6. Your problem statement is not very clear. Basically, this answer is nonsense. Code Review Stack Exchange is a question and answer site for peer programmer code reviews. 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. The most obvious solution to me is to use the key keyword arg. Do I need a thermal expansion tank if I already have a pressure tank? However, some may lead to under-performing solutions if not done properly. @RichieV I recommend using Quicksort or an in-place merge sort implementation. @Hatefiend interesting, could you point to a reference on how to achieve that? 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.
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sort list based on another list java 2023