In the above example, we have created an arraylist named numbers. Comic about an AI that equips its robot soldiers with spears and swords. What I am doing wrong? Thus, in the face of concurrent Thanks for contributing an answer to Stack Overflow! If you use classical for loop with the index or enhanced for loop and try to remove an element from the ArrayList using remove () method, you will get the C oncurrentModificationException but if you use Iterator's remove method or ListIterator's remove () method, then you won't get this error and be able to remove the element. Initialize an array with size of the number of odd elements. Remove even numbers from an ArrayList java collections arraylist 30,405 Solution 1 Use an Iterator. In the second case, you remove the 1 from the list during the first iteration, and the next iteration throws the exception when it tries to retrieve the next element. Do large language models know what they are talking about? Should i refrigerate or freeze unopened canned food items? ArrayList remove more than 1 per for loop? What is the purpose of installing cargo-contract and using it to create Ink! Making statements based on opinion; back them up with references or personal experience. What type of anchor is this and how do I remove/replace/tighten it? But in my case the situation did not merit such an optimization. If the list is not randomly accessible (does not implement RandomAccess) then you should use an iterator instead, as these types of collections usually take longer to retrieve an element at a specific index position, such as a LinkedList. If the current number is NOT the original input number, remove it from the array list. If the current number is NOT the original input number, remove it from the array 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. Does "discord" mean disagreement as the name of an application for online conversation? ", And I can't seem to be done with the second part (removing all multiples). In general, the results of the iteration are undefined under these circumstances. Do I have to spend any movement to do so? For instance, why does Croatia feel so safe? Modify objective function for equal solution distribution. How do I read / convert an InputStream into a String in Java? How Did Old Testament Prophets "Earn Their Bread"? In the above example, we have used the Java String contains() method to check if the element contains land in it. The cheapest (in terms of lines of code) way to remove duplicates is to dump the list into a LinkedHashSet (and then back into a List if you need). The below code will remove the even indexed numbers from the list: Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Those saying that you can't safely remove an item from a collection except through the Iterator aren't quite correct, you can do it safely using one of the concurrent collections such as ConcurrentHashMap. JVM bytecode instruction struct with serializer & parser, Asymptotic behavior of a certain oscillatory integral. How To Remove An Element From An Array Java? methods are fail-fast: if the list is structurally modified at any Can I knock myself prone? @ReynardJoseph that variable is part of a lambda expression which are available since Java 8. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, @omerhakanbilici This is only the default implementation. Here is my code: Is the executive branch obligated to enforce the Supreme Court's decision on affirmative action? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Can an a creature stop trying to pass through a Prismatic Wall or take a pause? "Removing" even numbers from array and moving odd to the front Remove the middle element if the array length is odd, or the middle two elements if the length is even. First of all - it's not a homework - I got this question at my last interview and wasn't able to finish it. If a single thread issues a sequence of method invocations that violates the contract of an object, the object may throw this exception. Even elements (like the title says) or even index numbers (like the question body says)? Initialize variable even with 2. In this article, you will see how to remove even numbers from an array by using Java programming language. Java List remove () Methods There are two remove () methods to remove elements from the List. 'Must Override a Superclass Method' Errors after importing a project into Eclipse. Efficiency of Java "Double Brace Initialization"? The only way around this is to use a CopyOnWriteArrayList, but that is really intended for concurrency issues. Making statements based on opinion; back them up with references or personal experience. Why is this? If you cast a spell with Still and Silent metamagic, can you do so while wildshaped without natural spell? Modify objective function for equal solution distribution, Lifetime components in phosphorescence decay, Verb for "Placing undue weight on a specific factor when making a decision". You must've caught me in a bad mood, but seems to me the answer to this question comes straight out of the foreach documentation. What's it called when a word that starts with a vowel takes the 'n' from 'an' (the indefinite article) and puts it on the word? @Ryan I have a problem, but not the one you indicated. Does this change how I list it on my CV? Foreach against for(int) loop - why does foreach raises exceptions when removing elements? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. So you can use this random: Here are the 2 changes required to make the program work: Here is the working solution, with these 2 changes: In your class ArrayExample method printMethod expect ArrayList as parameter, but in main method you try to pass ArrayDeque which is not compatible with ArrayList. While the next even number has a lower index than the next odd, swap them. Why does this Curtiss Kittyhawk have a Question Mark in its squadron code? Using java-8 and lamdba expressions, the method removeIf has been introduced for collections. The java design of the "enhanced for loop" was to not expose the iterator to code, but the only way to safely remove an item is to access the iterator. Java Program to Remove Even Numbers from Array - BTech Geeks One would point to the next even number (starting at the beginning), and one would point to the next odd number (starting at the end). Not a great plan. 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. langs.add (1, "C#"); This time the overloaded add method inserts the element at the specified position; The "C#" string will be located at the second position of the list; remember, the ArrayList is an ordered sequence of elements. How to deal with ConcurrentModificationException in Java? Beware while [Solved]-Remove even numbers from an ArrayList-Java What are the implications of constexpr floating-point math? How to remove elements in ArrayList through for loop using Java How to Remove Even Numbers from Array in Java - YouTube Note that the code calls Iterator.remove, not List.remove. Is there an easier way to generate a multiplication table? Yes. However to answer the question, you'd really need some code (as other answers have). Do large language models know what they are talking about? Removes all of the elements of this collection that satisfy the given Find centralized, trusted content and collaborate around the technologies you use most. Thank you. I tested it with { 5, 4, 3, 8, 6, 4, 9, 7,6 } and the result is { 5, 3, 9, 7, 6, 4, 9, 7, 6 }. Have ideas from programming helped us create new mathematical proofs? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Should I disclose my academic dishonesty on grad applications? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing. "Then we must be ready by tomorrow, must we?". Is there an easier way to generate a multiplication table? But I can't seem to find the connection. It starts with wrong index (zero), modifies the list on the fly and can easily generate IndexOutOfBoundsException. java - Remove multiple numbers from an ArrayList - Stack Overflow Can an open and closed function be neither injective or surjective. Do large language models know what they are talking about? This may be a bit more advanced than your class wants you to go right now, but the List interface provides a removeIf() method that allows you to remove all elements of the List that match a certain condition. It was worded kinda strange because they said remove but the examples showed that I should just put all odd numbers in front of the array (starting from 0-index) and even numbers can stay in the array (or not - it doesn't matter) after all the odd numbers. "Removing" even numbers from array and moving odd to the front. Just as a side-note, that should work fine with any base-class list, but wouldn't be portable to more esoteric structures (like a self-sorting sequence, for example--in general, anywhere the ordinal for a given entry could change between list iterations). Why is it better to control a vertical/horizontal than diagonal? Ltd. All rights reserved. Why are Java generics not implicitly polymorphic? When did a Prime Minister last miss two, consecutive Prime Minister's Questions? What is the purpose of installing cargo-contract and using it to create Ink! Let's explore. I would reverse the method, what i mean instead of removing the even i would move the odd ones into the front which is what they and they don't care of what is left in the array, so my approach would be like. Perhaps what is unclear to many novices is the fact that iterating over a list using the for/foreach constructs implicitly creates an iterator which is necessarily inaccessible. Thanks for contributing an answer to Stack Overflow! the main thing here is iterating in reverse order because iterating from index 0 to the end doesn't work. Note: since the array index starts from 0, after removing even indexes from 1,2,3,4,5,6,7,8,9,10 the output will be 2,4,6,8,10. Draw the initial positions of Mlkky pins in ASCII art. Equivalent idiom for "When it rains in [a place], it drips in [another place]". I would like to checking if an element is even or odd. Notice the line. @user15358848 as per my answer, it is not efficient, but its simple and gets the job done. iterating through the arraylist from the last to the first element and checking each index if it is even and removing the element at that specific index will do the trick. Developers use AI tools, they just dont trust them (Ep. The iterators returned by this class's iterator and listIterator Comic about an AI that equips its robot soldiers with spears and swords. still upvoted it, liked it from the beginning. Create a for loop, starting at 0, that adds the specified number to an index on every loop iteration. Program where I earned my Master's is changing its name in 2023-2024. (1) You need to return the list object (contains Integers) after the removal of odd numbers (2) In order to return the list, you need to change the method signature from int to List<Integer> (as return type): You can refer the below code with comments: Difference between machine language and machine code, maybe in the C64 community? I guess I would just maintain two variables pointing at locations within the array. Iterate the original array and insert the odd elements into the new array. 586), Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Testing native, sponsored banner ads on Stack Overflow (starting July 6), Temporary policy: Generative AI (e.g., ChatGPT) is banned, Arraylist(even/odd) swapping elements java, Array List for odd and even numbers stopping at -1, I want to print even and odd number from an input array list, Separating even and odd indexes from and ArrayList in Java using recursion, Returning all Odd numbers from an arraylist in java. How Did Old Testament Prophets "Earn Their Bread"? you have two problem, the first one is your argument is a string instead of an integer. Comic about an AI that equips its robot soldiers with spears and swords. Thomas's solution is good enough for this matter.. How can I move all even numbers to front in an array? 13 Answers Sorted by: 182 try this list.removeAll (Arrays.asList (2)); it will remove all elements with value = 2 you can also use this list.remove (Integer.valueOf (2)); but it will remove only first occurence of 2 list.remove (2) does not work because it matches List.remove (int i) which removes element with the specified index Share java - Remove even numbers from an ArrayList - Stack Overflow Lambdas are a more complex topic, but they're incredibly useful. I think it might be too advanced for myself atm. Such indexed based operations should only be conducted on lists whose elements can be accessed in O(1) constant time. How to resolve the ambiguity in the Boy or Girl paradox? How to generate a sequence created by removing all odd-indexed elements recursively from an Arraylist so that we get only 1 element at the end? Even numbers start from 2. Developers use AI tools, they just dont trust them (Ep. Why are lights very bright in most passenger trains, especially at night? How to install game with dependencies on Linux? Thank you for the input. The behavior of an iterator is Have you mastered basic programming topics of java and looking forward to mastering advanced topics in a java programming language? You can overcome this by decrementing your for loop iterator, which is a working solution, but not the best. 23 8 Add a comment 3 Answers Sorted by: 3 Because when you remove a item in the arraylist, you've changed the list, try to iterate it in reverse mode. Appreciate the input. I've updated my question with a little bit of an explanation. What do you want to remove? Removing object from ArrayList in for each loop. For example, if a thread modifies a collection directly while it is iterating over the collection with a fail-fast iterator, the iterator will throw this exception. Java ArrayList removeIf() - Programiz Why is the tag question positive in this dialogue from Downton Abbey? Does "discord" mean disagreement as the name of an application for online conversation? write the code to remove even numbers from Arraylist. I almost missed and used list.remove. Getting rid of a completely and just returning list will fix that issue. Its very slow. As other people have indicated, the problem is that you're returning this: Thus, you'll always get the first item in the list, regardless of what you do to it after you retrieve it.
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