If you like GeeksforGeeks and would like to contribute, you can also write an article and mail your article to See your article appearing on the GeeksforGeeks main page and help other Geeks. Retrieving Elements from Collection in Java (For-each, Iterator, ListIterator & EnumerationIterator) Iterator and for-each loop are faster than simple for loop for collections with no random access, while in collections which allows random access there is no performance change with for-each loop/for loop/iterator. But if the collection is LinkedList, then random access is not possible since it is not allocated contiguous memory blocks, so in order to access a element we will have to traverse the link list till you get to the required index, thus the time taken in worst case to access an element will be O(n). Here if the list l is an ArrayList then we can access it in O(1) time since it is allocated contiguous memory blocks (just like an array) i.e random access is possible. Here l is List ,it can be ArrayList /LinkedList and n is size of the List If you iterate using the old styled C for loop then we might increase the time complexity drastically. Here, by performance we mean the time complexity of both these traversals. Traversing a collection using for-each loops or iterators give the same performance. For each iteration, the current entry is assigned to the variable entry, and we can access the. Software Engineering Interview Questions The for-each loop is used to iterate over each entry in the map. ⢠Top 10 System Design Interview Questions and Answers The most basic and close-to-metal method of iterating over the set is invoking the iterator method exposed by every Set: Set names Sets.newHashSet ( 'Tom', 'Jane', 'Karen' ) Iterator namesIterator erator () Then we can use the obtained iterator to get elements of that Set, one by one.Top 20 Puzzles Commonly Asked During SDE Interviews.Commonly Asked Data Structure Interview Questions.Top 10 algorithms in Interview Questions.Top 20 Dynamic Programming Interview Questions.Top 20 Hashing Technique based Interview Questions.Top 50 Dynamic Programming (DP) Problems.Top 20 Greedy Algorithms Interview Questions.Top 100 DSA Interview Questions Topic-wise.If you, however, need to access the index to edit the next or previous element, it may make more sense to use the for loop or the while loop. The iterator automatically counts through the array or list and terminates the loop when all elements have been traversed. The for-each loop internally uses an iterator to call up each element of the array or list one by one. Not having to consider these aspects means you avoid the risk of an index being outside of the valid range. In contrast to the for loop in Java, when you use the for-each Java loop, you donât need to consider the index or size of the array. In each iteration, you can perform automatic manipulations with common Java operators without having to write a separate statement for each element. The for-each loop can likewise be used to iterate through elements in a list implemented as an ArrayList. For example, a common use is to output or search for specific elements of an array. The for-each loop is used in many scenarios where Java developers need to work with arrays. What is the for-each Java loop used for? ¶
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