Java Collections Framework Tutorials

The Java Collections Framework is a collection of interfaces and classes which helps in storing and processing the data efficiently. This framework has several useful classes which have tons of useful functions which makes a programmer task super easy. I have written several tutorials on Collections in Java. All the tutorials are shared with examples and source codes to help you understand better.

Java Collections – Table of Contents

1. ArrayList
2. LinkedList
3. Vector
4. HashSet
5. LinkedHashSet
6. TreeSet
7. HashMap
8. TreeMap
9. LinkedHashMap
10. Hashtable
11. Iterator and ListIterator
12. Comparable and Comparator
13. Java Collections Interview Questions

Collections Framework hierarchy

Java Collections

Java Collections – List

A List is an ordered Collection (sometimes called a sequence). Lists may contain duplicate elements. Elements can be inserted or accessed by their position in the list, using a zero-based index.

ArrayList

Here is the list of all the tutorials published on the ArrayList.

ArrayList Basics

ArrayList Sorting

ArrayList Add/Remove

Get/Search in ArrayList

Other Tutorials on ArrayList

ArrayList Conversions:

Differences:

LinkedList

Here is the list of all the tutorials published on the LinkedList.

LinkedList Basics

LinkedList Add/Remove

Get/Search in LinkedList

LinkedList Iterator/ListIterator

Other Tutorials on LinkedList

Conversion

Vector

Here is the list of all the tutorials published on the Vector.

Vector basics

Remove/Sort/Replace in Vector

Vector -Iterator/ListIterator/Enumeration

Conversions

Java Collections – Set

A Set is a Collection that cannot contain duplicate elements. There are three main implementations of Set interface: HashSet, TreeSet, and LinkedHashSet. HashSet, which stores its elements in a hash table, is the best-performing implementation; however it makes no guarantees concerning the order of iteration. TreeSet, which stores its elements in a red-black tree, orders its elements based on their values; it is substantially slower than HashSet. LinkedHashSet, which is implemented as a hash table with a linked list running through it, orders its elements based on the order in which they were inserted into the set (insertion-order).

HashSet

Here is the list of all the tutorials published on the HashSet.

LinkedHashSet

TreeSet

Java Collections – Map

A Map is an object that maps keys to values. A map cannot contain duplicate keys. There are three main implementations of Map interfaces: HashMap, TreeMap, and LinkedHashMap.
HashMap: it makes no guarantees concerning the order of iteration
TreeMap: It stores its elements in a red-black tree, orders its elements based on their values; it is substantially slower than HashMap.
LinkedHashMap: It orders its elements based on the order in which they were inserted into the set (insertion-order).

HashMap

Here is the list of all the tutorials published on the HashMap.

HashMap Basics

  1. HashMap in Java
  2. How to iterate HashMap
  3. Sort HashMap by Keys and values
  4. Get Size of HashMap
  5. Remove Key-value mapping from HashMap
  6. Remove all mapping from HashMap
  7. How to check if HashMap is empty or not?

Get/Search in HashMap

  1. Check if particular key exists in HashMap
  2. Check if particular value exists in HashMap

Serialize/Synchronize

  1. Serialize HashMap
  2. Synchronize HashMap

Differences

  1. HashMap vs Hashtable
  2. HashSet vs HashMap

Other Tutorials on HashMap

  1. HashMap Iterator example
  2. Copy one HashMap to another
  3. Get value from HashMap using Key
  4. Get Set view of keys from HashMap
  5. Clone a HashMap

TreeMap

LinkedHashMap

LinkedHashMap in Java

Hashtable

Hashtable in Java

Java Collections – Iterator/ListIterator

Both Iterator and ListIterator are used to iterate through elements of a collection class. Using Iterator we can traverse in one direction (forward) while using ListIterator we can traverse the collection class on both the directions(backward and forward). To know more differences between these two refer this article: Difference between Iterator and ListIterator.

Comparable and Comparator Interfaces

These interfaces are used for sorting objects of user defined class (custom class).

Collections Interview Questions

Collections Framework Interview Questions

Reference: Official Document on Collections

Comments

  1. Hi Sir,
    I thank you very much for posting such an awesome java content.
    The way you explained the Concepts are very clear.
    But I am not able to find topics on List and Set.
    Could you please let me know the link for accessing the List and set related topics ?

    Rgds,
    Manvi

    Reply

    • Thank you for your kind words. I have updated the page by providing links of List and Set related tutorials, you can find the same above.

      Reply

  2. Hi sir,

    This site is simply awesome.Thanks for your efforts.
    we need more concepts from you like struts,hibernate ….!

    Reply

  3. Hai Sir,
    This site is very useful for learners.I had one doubt, the doubt is, in hashmap and array concept we will display line and bar graph in one page with data input and cluster in JSP.what is the source code .Kindly tell me.Please send source code in my mail.
    Thank you.

    Reply

  5. Hi Chaitanya,
    Your content,depth of knowledge in the concepts is simply superb,mind blowing and awesome,i have visited many blogs and sites to learn the concepts in a easily understandable way, but i didn’t find any, but when i came across your site accidentally, i was amazed by way you make readers understand the concepts.
    All these years i was feared of looking at the concepts of collections even,but now, after going through your site. That fear in me no more exist!!!! I thanks you from my bottom of heart for your kind knowledge sharing.

    Regards,
    Sriram.

    Reply

  6. I was looking for this kind of organized concept based tutorial on the Internet for an hour. indeed I succeeded! thank you sir! do you also have tutorials on JSF, hibernate, EJP, JPA, Spring, struts ? I really need to learn this topics from you if it is available. keep the good work!

    Reply

    • Hi kalkidan,

      Iterator is used to iterate the element in one direction.
      It’s having three method.
      1. boolean hasNext( )
      2. Object next( )
      3. void remove( )

      The best example you can use Iterator is

      List list = new ArrayList();
      list.add(object1)
      list.add(object2);

      Iterator it = list.iterator();
      while(it.hasNext() ){
      Object obj = (Object)it.next();

      }

      Reply

    • Not all Collections provide index-based access, so we cannot always use while and do-while. There is an enhanced version of ‘for’ that can be used without index access.

      In cases, where there is no index based access (i.e. set), we use an Iterator, otherwise it use your choice to choose the iteration method if the index is available to you.

      Reply

  8. Great work buddy !!!!
    I learned lot of thing from your site. Your explanations are very simple and clear.
    keep it up.
    best of luck !!!

    Reply

  10. Hello Chaitanya, this tutorial is awesome. Many thanks for your efforts. Do we option to post our java queries in this site? If Yes, please let me know. If not, I think it would be a great enhancement for this site.

    Reply

  11. Just one word..Brilliant tutorials.You helped me remove my fear over collections. I am thankful to you very much
    Keep posting more tutorials

    Reply

  12. Hi Sir,

    the way your explanation is very very good, Beginners book is exactly suitable word for people who are learning new technology this website is 100% perfect for learners

    Reply

  15. The content is very simple but yet very strong in communicating the concepts. Excellent set of tutorials.
    Thanks a lot!!

    Reply

  16. Hi Chaitanya!
    Very good job.One of the best collections examples I have seen till date.Keep up the good work.All the best for all your future endeavors!

    Reply

  21. Absolutely awesome site for beginner…..
    Most of java interview will ask question on JAVA COLLECTION FRAMEWORK,,, this site helps me lot…. thank you very much….

    Reply

  22. Really awesome site……each and every concept explained with very easy and simple example .for me you made collection is very easy.
    Thank you so much for your efforts :)

    Reply

  23. By far, this is the best website that I found easy for learning the concepts in Java. All the concepts are explained in a manner that it’s can be grasped quite easily. The topics seem to be very clear.

    THANK YOU!! I’ll definitely recommend this site to my friends.

    Reply

  24. superb…explanation with perfect matching examples. This is the best blog forever for COLLECTIONS concepts compare to others……..

    Reply

  25. This site is really awesome. Now my all concepts are cleared regarding the Collections. It would be awesome if you provide tutorial for Spring, Struts and Hibernate too.

    Reply

  27. That’s really good job.Well done.Everything has been expained very clear and the examples has wrapped your theoritical parts in a great way.A good tutorial not only for beginners.Carry on the good job.

    Reply

  28. In collection framework we have a class called “Stack”, i didn’t find it in diagram can you explain about this.

    Reply

  29. Hi bro your site really good particularly in collection section. Previously I dont known about collection but after saw your site I learnt collections part from your site. It was very much helpful to me. The same way I expecting Spring, SpringMVC, Hibernate from you.

    Reply

  30. hello sir …
    this tutorial very help full to me . and want to learn spring framework
    if you know please tell me or any good spring reference link send to my mail…
    thankyou sir….

    Reply

  31. I just started learning Java . The Problem I faced initially was too many content in the internet. But your example seems to be one stop shop where I can get everything at one place. Keep Uploading the new topics in similar way. Just a advise , why dont you start Youtube channel ,you can explain theoretical concepts also :)

    Reply

  34. Thank You for giving a clear & precise understanding of Collections Framework. You have literally removed my fear of Collections. Keep up the Good Work. Thanks once again from the bottom of my heart!!!:)

    Reply

  35. Probably your best source for information on the Stack class is Oracle.com for the version of Java you are using. It will act similar to the other collection classes described here.
    P.S. Nice job of explaining collection classes. I really like ArrayList because it dynamically grows as elements are added, eliminating array out of bounds exceptions. Thanks, Brent

    Reply

  36. Sir i really like ur site and its content, everything is very organized and detailed, every topic is being covered with fine details. for a beginner this site is very useful,i request u sir to please introduce such type matter for data structure also.please

    Reply

  37. hi sir
    your site is simply superb and easy to learn java! especially collections are very easy to understand and examples are really awesome! compared to other
    sites this one is very nice and easy to learn! :)

    Reply

  38. if collection is an interface and list also being an interface then..what i understand is list implements collection …but i also know that interface cannot implement another interface…than what is the justification for this?

    Reply

    • List is interface .
      Collection is interface .

      one interface always extends another interface .

      so List extends Collection

      Reply

  42. Hi ,
    Hash Map can contain duplicate key values. Please correct it.
    Great Job !! The Beginner’s book is one of the best sources to learn and make concepts clear.Thank you very much for your efforts.

    Swetha.

    Reply

    • HashMap can contain only one null key (and that key cannot have any value, because you can’t access the null key!). So having a null key as good as useless.

      Reply

  44. hello….sir

    your tutorial is nice,can you tell me where is the use of collection in project and how?

    Reply

  46. Hi Chaitanya, this beginners book has helped me a lot to grasp java concepts so easily. Your passion for java is making way for lots to understand these vast/complex java concepts more easily. You have structured tutorials for each and every topics soo nicely that only after reading this we can get clear understanding of each and every topic to implement them in practice. Thanks a lot for putting your passion into internet where it is helping us to grow our career.

    Reply

  48. Hello All,

    Could you please provide me link to follow the Spring Framework tutorials.

    Thanks and Regards,
    Uma Shankar Gupta

    Reply

  49. Hai Chaitanya,

    Iam a HardCore fan of this Beginners Book . I would like to know about Colletion in depth. Queue Interface and some of the concepts are not provided.Could you please Provide all Collection Topics.

    Thanks&Regards
    Uday Kumar Mashetti.

    Reply

  50. Hi Chitanya,
    Awesome explanation on collections…looking forward for explanations about ConcurrentHashMaps,etc thru you.

    Thanks
    Priya M

    Reply

  51. Hello Chaitanya,

    You have not provided tutorials for “HASHTABLE”.
    Could you please provide the same?

    Regards,

    Rajnayan

    Reply

  52. Hi Chaitanya,
    Please correct this – TreeMap: It stores its elements in a red-black tree, orders its elements based on their VALUES.

    It should be “orders its elements based on their KEYS”

    Excellent article, thanks a ton!

    Reply

  54. HI Chaitanya
    You did a brilliant job on Beginnersbook’s Collection Framework. I appreciate you for such a best study content.
    Thank you Sir.

    Reply

  56. Hi, This site contents are very clear and given neat explanation about collection framework. As a beginner, This site could be very useful. thank you for your effort to making this blog and it will be very helpful us to learn about collection. We were expecting more updates on collection framework.

    Thank you!..

    Reply

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