UPDATE: As per VisioN's comment, a simple for loop would get the same job done more efficiently, and it is easier to understand and therefore easier to maintain: Another alternative solution is to use Array.prototype.reduce(): N.B. This will give you the first match when there are multiple duplicates. The neuroscientist says "Baby approved!" Who was the intended audience for Dora and the Lost City of Gold? Overloads can be added for int[], long[], etc. Has a bill ever failed a house of Congress unanimously? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing. Object.equals is a virtual method defined for all object instances and it means "has the same value", as all class types extend Object, and should be used for all object-equality tests. In this tutorial, we'll demonstrate a simple algorithm that uses the indexOf (String str, int fromIndex) method of the Java String class to find all occurrences of a word within a string. Simple Algorithm EDIT: Updated to a geometrically decreasing sum instead of increasing. When you do this you can use the methods indexOf and contains of the ArrayList like this: arrayList.indexOf(new AuctionItem("The name")). rev2023.7.7.43526. Is there any way of combining the hashmaps commands? "Indices" and "indexes" are both correct, and I tend to alternate between the two. Not the answer you're looking for? Find centralized, trusted content and collaborate around the technologies you use most. @CoolCloud Sure, if you know that index beforehand already but if your suggesting to use something like. @NewJavaStudent Never do a for(i) loop on a LinkedList. Why free-market capitalism has became more associated to the right than to the left, to which it originally belonged? Connect and share knowledge within a single location that is structured and easy to search. Please write an essential explanation or inline comments for the code. Example: Now, I would like to the get the index of an Object which contains the name as "Girish". Asking for help, clarification, or responding to other answers. Actually i would like to update that particular object when an update came from the server. @Zabuza you should read my solution again - it does collect the indexes. Connect and share knowledge within a single location that is structured and easy to search. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Find the index of a prime number in an array, Changes to already-visited indexes do not cause, If an existing, yet-unvisited element of the array is changed by. I thought you wanted to actually have different values, or store things in buckets. If you read this far, tweet to the author to show them you care. Yes to the loop (either using indexes or an Iterator). Seems to me that OP actually wants a single number as output (assuming he/she can't figure out that he/she can change the push to. No, I'm not. Therefore: Warning: Concurrent modifications of the kind described above frequently lead to hard-to-understand code and are generally to be avoided (except in special cases). Why do complex numbers lend themselves to rotation? The parameter for this function is an object. There were just so many sprawling for loops I thought, "I could make my own answer in 2 seconds.". Method 1: Use the indexOf () Method to Find Index We can easily find the index of a specific list element using the indexOf () method. int indexOf(Object o) This method returns the index in this list of the first occurrence of the specified element, or -1 if this list does not contain this element. Find centralized, trusted content and collaborate around the technologies you use most. So we invoke orElse(-1) to either return the value found or -1 if none were found. How did the IBM 360 detect memory errors? The get () method of ArrayList in Java is used to get the element of a specified index within the list. The index of the first element in the array that passes the test. To learn more, see our tips on writing great answers. Substring: get index of "or" occurrence in string, How to replace second occurence of char in a String? This is O(n). The indexOf method returns the index position of a specified character or substring in a string. What is the reasoning behind the USA criticizing countries and then paying them diplomatic visits? delimiter is not working. How to find the index of an element in an int array? See : great, it works. At the end, i need all these objects in a list to do some analytics. How to format a JSON string as a table using jq? Also, if u want to find all indexes of a String in a String. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, Good question MC. Introduction In this article, we'll learn different approaches to finding duplicates in a List in Java. My manager warned me about absences on short notice. Indexes of all occurrences of character in a string, Why on earth are people paying for digital real estate? Just use that indexOf string function and you could find any character within any alphabet ( or array of characters ). Not the answer you're looking for? That's not even valid syntax. For example: int myIndex = list.indexOf ("Ram") (Note though that your arraylist doesn't contain "Ram", it contains an object of type MyObj with a name of "Ram") Bear in mind ArrayLists start at 0 not one. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Note: MDN gives a method using a while loop: I wouldn't say it's any better than other answers. I should have seen yours before I spent time writing mine. Not the answer you're looking for? However, the conditions that would favor using such an approach do not seem to be present. Find centralized, trusted content and collaborate around the technologies you use most. This example will help us understand the public int indexOf(int char) method. How can I find the following Fourier Transform without directly using FT pairs? Note that when a substring is passed in as a parameter, the index returned is the index of the first character in the substring 11 is the index of the "b" character. How to get index of all occurrence of the same value in an Array? Languages which give you access to the AST to modify during compilation? Further, there are other solutions (e.g. Also note that calling List#contains is not necessary since List#indexOf also answers this question, it returns -1 if not found. Do you need an "Any" type when implementing a statically typed programming language? What is the fast way of getting an index of an element in an array? You can always loop through the list manually: Thanks for contributing an answer to Stack Overflow! Can ultraproducts avoid all "factor structures"? It calls a provided callbackFn function once for each element in an array in ascending-index order, until callbackFn returns a truthy value. Find centralized, trusted content and collaborate around the technologies you use most. Air that escapes from tire smells really bad. I tried the following example, which does not work: Can anyone please explain what is wrong with this and what I need to do to fix it? Were Patton's and/or other generals' vehicles prominently flagged with stars (and if so, why)? rev2023.7.7.43526. BCD tables only load in the browser with JavaScript enabled. I want to set a weight factor p^i for each position i of this list. I think he wants to collect the indices, not the elements (since they are equal). Making statements based on opinion; back them up with references or personal experience. Languages which give you access to the AST to modify during compilation? how to determine the optimum FL for A320 to make a flight plan? How can I learn wizard spells as a warlock without multiclassing? A value to use as this when executing callbackFn. How to find index position of an element in a list when contains returns true, Why on earth are people paying for digital real estate? Do you need an "Any" type when implementing a statically typed programming language? This website uses cookies. Two approaches to this problem: 1- Don't use ArrayList, Use HashMap<String,AutionItem> where String would be name. Imagine you have 10 drawers, numbered from 0 to 9, and want to find all the drawers containing a blue sheet of paper, and write their number on a sheet of paper. Do I have the right to limit a background check? developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/, Why on earth are people paying for digital real estate? Java 8's steams give you a pretty elegant way of doing this: Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. rev2023.7.7.43526. 1. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, It doesn't seem to be the faster alternative to a single, @VisioN - Yes, a plain for loop iterating over the array would be simpler too, but since the OP mentioned trying to use. Please add some explanation to your answer such that others can learn from it. A function to execute for each element in the array. As JB Nizet said, there's a bigger question to be tackled here. The community reviewed whether to reopen this question 9 months ago and left it closed: Needs more focus Update the question so it focuses on one problem only by editing this post. How to find the index of matching string in a list java? Why add an increment/decrement operator when compound assignnments exist? The problem with your code is that when you do. For object arrays, like String[], we could use the same idea and have the filtering step using the equals method, or Objects.equals to consider two null elements equal, instead of ==. Any suggestion? If you are just using JavaScript, null works fine. Okay - seems like a school assignment, so I will be very high level to help with the logic. Not the answer you're looking for? I assume when I call random.nextInt() I pass a zero argument (as indicated by the previous thread Exception in thread "main" java.lang.IllegalArgumentException: n must be positive), but how is this possible, since my argument is minKeyList.size()? Rather than a brute force loop through the list (eg 1 to 10000), rather use an iterative search approach : Connect and share knowledge within a single location that is structured and easy to search. Indexes are zero-based, so this will fail if the first car is a Nano. It returns an index from a specified position. How to format a JSON string as a table using jq? You'll want to iterate over the contents in order to do the check you want: This way should work, change "char" to "Character": is an string object literal ( which represents an string object that is ), Is a character literal ( which represents a character primitive datatype ). Brute force open problems in graph theory. My problem is: How to get ALL the indexes where these elements (ID 4 and ID 5) are located in the list in order to calculate the value of these elements as the sum of the associated with these indexes weighting factors? We have two "o" characters but the index of the first one got returned. How can I learn wizard spells as a warlock without multiclassing? How to play the "Ped" symbol when there's no corresponding release symbol, Number of k-points for unit and super cell. Why add an increment/decrement operator when compound assignnments exist? Here server will give updates for individual objects only. How about iterating and updating a temporary sum. p = 1/2). how to determine the optimum FL for A320 to make a flight plan? 587), The Overflow #185: The hardest part of software is requirements, Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned, Testing native, sponsored banner ads on Stack Overflow (starting July 6). Funny coincidence: I just edited my reply to your comment under my answer to suggest exactly this solution, then I refresh and see you'd already coded the same thing with only one variable name different. Just a minor comment, in a bottleneck piece of code it's recommended to run list search only once: what about an example? 1. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Wouldn't it be better to start from first index of occurrence of item rather than from 0th position? findFirst returns an OptionalInt, as it is possible that no matching indexes were found. I strongly recommend wrapping the map in some object and use generics if possible. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Get index of contain sublist from list java, Java: Find the index of a String in a list, Searching Point in a list by its position. @S.R.I I think it's a fine question. Using this method, you can find the index of a given element. Can you also write here the full implementation to add to the project? (Ep. Do United same day changes apply for travel starting on different airlines? What does "Splitting the throttles" mean? 2. Trying to find a comical sci-fi book, about someone brought to an alternate world by probability. Donations to freeCodeCamp go toward our education initiatives, and help pay for servers, services, and staff. How to find the index of matching string in a list java? The indexOf () method of ArrayList returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element. Below is the sample code to check an element in the List by using contains () method. If, Did you even try running this code? It is of data-type int. Let us now assume that I have the following items in the list, from position 0 to position 4 (I give the IDs of these items): 4 | 4 | 5 | 4 | 5. By using this site, you agree to the use of cookies, our policies, copyright terms and other conditions. This should print the list of positions without the -1 at the end that Peter Lawrey's solution has had. How to get index of all occurences of the same value in an Array? Please do let me know the code in JAVA. This does not answer the question. It will print out every position (0, 1, 2, ) until the index of the last occurrence of.

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