Category: How to iterate nested list in java

Iterate through List Java example shows how to iterate over a List using for loop, enhanced for loop, Iterator, ListIterator, while loop and Java 8 forEach. We have added several Employee objects to our ArrayList. There are several ways you can iterate over a List or List implementations like the LinkedList or an ArrayList as given below. This is the simplest approach of all. You can use a for loop and loop from index 0 to the size of the list — 1 and access the list elements as given below.

Maintain the list index in a separate variable and increment it each time you access the list as given below. This example is a part of the Java ArrayList tutorial. My name is RahimV and I have over 16 years of experience in designing and developing Java applications. Over the years I have worked with many fortune companies as an eCommerce Architect.

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Please type your message and try again. This discussion is archived. Hi, How to iterate nested lists in java? I have the same question Show 0 Likes 0. This content has been marked as final. Show 11 replies. This is an example No it's not. There's no nested lists in your example. Only 3 different lists that seem to be sharing some of the elements. Nested lists means that lists contain other lists.

So rethink your question and surround your code with tags for proper formatting. Here I have list3 which contains list1 and list2so how can I get the values from list1 and list 2 by iterating list3? Please let me know your opinion? Start with trying to compile the code you posted it won't. The compiler errors should give you the idea what is wrong with your code. Here I have list3 which contains list1 and list2 No you don't.

It contains the contents of list1 and list2. There's a significant difference. So how can I get the values from list1 and list 2 by iterating list3? If your current code would compile, you could get the values normally, by iterating list3. However if you're looking to iterate nested lists, then you need additional for loops to iterate the inner lists. Also please try to post a SSCE example. This will give you an idea of the contents of list3. Thanks Guys. Now guys tell me how i can have 2 for loops to do a nested loop iteration.

Please provide some links or site which will be helpful. Thanks Mohammad, I am unable to find a suitable example for List of list objects. Please provide me an example which will be of great help. Otherwise there are compilation issues with the code you posted in your first post, correct them as well. You mean list3 contains the lists 1 and 2?By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. How can I iterate this? My hibernate query is:. The Object[] arrays contain one element per requested field.

In your case, each Object[] will contain franchiseId at index 0 and resellerId at index 1. This is of course explained in the reference documentation.

Learn more. How to iterate over a nested list Ask Question. Asked 8 years, 7 months ago. Active 8 years, 7 months ago. Viewed 4k times. Mike Samuel k 26 26 gold badges silver badges bronze badges. Khoyendra Pande Khoyendra Pande 1, 3 3 gold badges 25 25 silver badges 41 41 bronze badges.

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Iterate Over A List or Set in Java 8

To iterate nested lists, you simply nest for loops. Jeremy Jeremy ClassCastException: [Ljava. Object; cannot be cast to java. Khoyendra: See JB Nizet's answer for why you're not getting what you expect. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Q2 Community Roadmap. The Unfriendly Robot: Automatically flagging unwelcoming comments.

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Given a nested list of strings which may contain other nested listsprint the contents of the list and the corresponding depth. I am not that much interested in naming of the variables, but of formatting of the output. Should I print it differently? The dumpList method takes a Listand then you make 2. Keep in mind that the List interface doesn't ensure random access.

For example I can call this method with a LinkedList parameter, in which case the. Either change the method parameter to ArrayList or similar random access list, or change the way you iterate I recommendfor example like this:. Instead of doing if item instanceof String and then if item instanceof Listit's better to do if item instanceof List and an else.

This solves 2 problems at once:. Adds support for other element types, not only String and List, which otherwise would have been ignored. The second if should have been either an else if or an elsebecause if the first if was true, it's pointless to evaluate the second.

Finally, I renamed l to list. Single-letter variable names are acceptable as loop counters, like i, j, k, otherwise it's better to give meaningful names. If performance is an issue, then yes, use StringBuilder see here. Another advantage of this approach is, that you are separating the collection of the data from the printing of the data. It would be easy to change the print command with for example a command to print to file later on.

The second version is a bit more readable, while the first version might be faster, depending on the Java implementation. That is really your decision. I think that the way you are doing it is a bit confusing, I would at least add a space in the recursive call between string and i so Foo12 becomes Foo1 2.

how to iterate nested list in java

Personally, I would prefer the output to look something like this: ["a string" 0["a" 1"b" 1"c" 1 ], "spam" 0"eggs" 0 ] where the numbers are the depth levelbut it really depends on what you want to do with the code. Also, right now, you are not printing the corresponding depth of the item you are printing each position inside the depth-level.

To do this, you would need another argument which you can increase every time you call dumpList :. Use generics better. Is it really important to be a List specifically? No, all you care about is that it is Iterable.

Which will also support this method for Set s and other Collection s, and even some other types. Iterable is more generic than only Collection. Sign up to join this community. The best answers are voted up and rise to the top.

Home Questions Tags Users Unanswered.Background : Iterator is an interface provided by collection framework to traverse a collection and for a sequential access of items in the collection. For each loop is meant for traversing items in a collection. Note : In Java 8 using lambda expressions we can simply replace for-each loop with. Modifying a collection simply means removing an element or changing content of an item stored in the collection. In the above code we are calling the next method again and again for itr1 i.

Now we are advancing the iterator without even checking if it has any more elements left in the collection in the inner loopthus we are advancing the iterator more than the number of elements in the collection which leads to NoSuchElementException.

Replace the iterator code with the below code.

how to iterate nested list in java

Traversing a collection using for-each loops or iterators give the same performance. Here, by performance we mean the time complexity of both these traversals.

2D Lists & Nested Loops - Python - Tutorial 24

If you iterate using the old styled C for loop then we might increase the time complexity drastically. 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.

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.

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How can I iterate this? My hibernate query is:. The Object[] arrays contain one element per requested field. In your case, each Object[] will contain franchiseId at index 0 and resellerId at index 1.

This is of course explained in the reference documentation. How are we doing?

how to iterate nested list in java

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How to Iterate through LinkedList Instance in Java?

Asked 8 years, 7 months ago. Active 8 years, 7 months ago. Viewed 4k times. Mike Samuel k 26 26 gold badges silver badges bronze badges. Khoyendra Pande Khoyendra Pande 1, 3 3 gold badges 25 25 silver badges 41 41 bronze badges. Active Oldest Votes.

To iterate nested lists, you simply nest for loops. Jeremy Jeremy ClassCastException: [Ljava. Object; cannot be cast to java. Khoyendra: See JB Nizet's answer for why you're not getting what you expect. Sign up or log in Sign up using Google. Sign up using Facebook.All of the operations perform as could be expected for a doubly-linked list.

Operations that index into the list will traverse the list from the beginning or the end, whichever is closer to the specified index. Note that this implementation is not synchronized. Get latest update on and. Join Over 16 Million Monthly Readers Thanks for your feedback Guwox. How it defeats purpose of LinkedList.

how to iterate nested list in java

Could you please share some more details? First, thanks for the posting. It was very useful. I have a follow up question regarding how to iterate using some of the linkedlist methods such as peek or remove.

I tried using peek method using the iterator but it follows in an infinity loop. I was wondering if you can iterate throw a LinkedList in java without using an iterator.

Something like : currentElement. Thanks but I meant treating an element of the LinkedList like a node with a previous and next attribute, without using the iterator. Your email address will not be published. LinkedList. ListIterator. ListIterator Approach :. Loop Approach :. Java8 Approach :. Other Popular Articles