CodeGym/Java Course/Module 1. Java Syntax/Additional lessons for Level

Additional lessons for Level


You already know a lot about primitive types, and in this level you got acquainted with their doppelgangers — the wrapper classes, and learned what autoboxing and unboxing are, how to compare wrapper types correctly, and how to do it incorrectly.

You also took your array experience to the next level by getting to know the ArrayList class. Basically, you've got stuff to think about! Better yet, set aside half an hour for a few additional articles on these topics that will put everything in its place.

Wrapper Classes in Java

The wrapper classes look and behave like the primitive type of the same name, but they are in fact real classes. This article expounds on who needs them, what they are for, and what you do with them.

Autoboxing and Unboxing in Java

In Java, a feature of primitives and their wrappers is autoboxing / unboxing. Let's dig into this concept.

ArrayList class

Arrays are great, but programmers get into a bad mood due to their limited size and the inability to add or remove new elements. So, meet ArrayList: it's a souped-up array, a simple and convenient data structure. Once you have moved from arrays to ArrayList, you just can't go back.

Deleting an element from an ArrayList

And here is another article that continues our discussion of ArrayList. This time we will dwell in more detail on important operations for working with lists — removing an item from a list, and removing an item from a list in a loop.

ArrayList in pictures

If you don't fully understand how ArrayList works, this lesson is for you. There will be a lot of pictures and explanations and almost no code. But most importantly, after reading and understanding it, you will understand very well how ArrayList works... Who knows, maybe you'll even implement your own after that! So, to advance your training, this is a good task for a beginning developer.

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Level 18 , Bangalore, India
28 November, 03:38
No mention of multidimensional ArrayLists?
b n raju
Level 15 , irving, United States
15 June, 20:06
need to know answers as well
Fadhil Radhian Software Engineer at Accenture
25 March, 02:55
needs to show the correct answer or option to retry
BoomShockPow Enterprise Java Developer
9 February, 18:35
Would love to know WHY I got these wrong.. Can't even retry the questions SMH
Hiyo Full Stack Developer
25 January, 13:54
Some Tips for the tricky ones 1. ArrayList objects can always modify its contents even if it's marked as final. 2. To insert, you just need to know the position and the "value" you want to insert. 3. To remove, you just need to know what "value" you want to remove. 4. ArrayList is part of List which is part of Java's Collection library and they use "size()" method, not length. Think of "length" for constant immutable like "array", "String" etc.
Tasmoda Android Developer
13 May 2022, 12:12
It would also be nice to have a retry at the questions I got wrong at the end of the quiz.
Level 50 , Kraków, Poland
16 November 2022, 16:27
Exactly, at least may be learn what was wrong and why.
Level 18 , Bangalore, India
28 November, 03:39
You can refresh the screen and retake the test.
Level 14 , Germany, Germany
29 April 2022, 12:06
It would be really nice to get the correct answers at the end, not just what question we did wrong.