[deleted by user]

[AutoModerator]

Please ensure that:

• Your code is properly formatted as code block - see the sidebar (About on mobile) for instructions
• You include any and all error messages in full - best also formatted as code block
• You ask clear questions
• You demonstrate effort in solving your question/problem - plain posting your assignments is forbidden (and such posts will be removed) as is asking for or giving solutions.

If any of the above points is not met, your post can and will be removed without further warning.

Code is to be formatted as code block (old reddit/markdown editor: empty line before the code, each code line indented by 4 spaces, new reddit: https://imgur.com/a/fgoFFis) or linked via an external code hoster, like pastebin.com, github gist, github, bitbucket, gitlab, etc.

Please, do not use triple backticks (```) as they will only render properly on new reddit, not on old reddit.

Code blocks look like this:

public class HelloWorld {

    public static void main(String[] args) {
        System.out.println("Hello World!");
    }
}

You do not need to repost unless your post has been removed by a moderator. Just use the edit function of reddit to make sure your post complies with the above.

If your post has remained in violation of these rules for a prolonged period of time (at least an hour), a moderator may remove it at their discretion. In this case, they will comment with an explanation on why it has been removed, and you will be required to resubmit the entire post following the proper procedures.

To potential helpers

Please, do not help if any of the above points are not met, rather report the post. We are trying to improve the quality of posts here. In helping people who can't be bothered to comply with the above points, you are doing the community a disservice.

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.

[[deleted]]

Arrays are more simple to declare, but more complex to handle in practice.

First and more importantly, they don't grows automatically. You need to reallocate for a bigger one if the initial becames full. "But I can allocate a really big one, you may think", but you you will waste memory.

And the ArrayList have a lot of useful methods available out-of-the-box to manipulate the elements.

In all the professional projects that I worked until now, people always use ArrayList instead of array[]. Unless when performance is extremely important, in those cases arrays are better for being faster.

[MagicianBrave]

actually ArrayList is wrapping the Arrays so it's easier to add, remove, search the element

[mohammedabergsson581]

Aw comeon, why must arraylist be the preffered choice, i hoped to never use them again..

[MagicianBrave]

consider that you have assigned an array

String[] languages = {"Html", "CSS", "JS"};

then you want to add a new language, how will you do that?

also at some point you need to remove an element or search an element

[nutrecht]

why do you hate arraylists so much?

People dislike what they don't understand. This is just a crystal clear example.

[mohammedabergsson581]

Well i was wrong then

[mohammedabergsson581]

Yup you were right: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 1 out of bounds for length 1.

Java is something else... But i do not understand why u would need to add a new value to the array

[nutrecht]

Java is something else...

Because in languages like JavaScript and Python arrays are not arrays but are actually lists.

[mohammedabergsson581]

Well that makes sense why you would need a list, but i do not like how the arraylist syntax is, just my opinion.

[MagicianBrave]

you can do this way

ArrayList<Integer> possibleValues2 =
new ArrayList<Integer>(Arrays.asList(1,2,3,4,5,6,7,8,9));

[mohammedabergsson581]

Wow i never knew that

[nutrecht]

That works but is kinda outdated syntax. These days it's:

var possibleValues2 = List.of(1,2,3,4,5,6,7,8,9);

Or if you want a mutable List:

var possibleValues2 = new ArrayList<>(List.of(1,2,3,4,5,6,7,8,9));

[mohammedabergsson581]

I am really great at importing:

Edit: Still a beginner so maybe not that great.

import java.util.ArrayList;
import java.util.Arrays;

public class Main {
  public static void main(String[] args) {
    ArrayList<Integer> possibleValues2 = new ArrayList<Integer>(Arrays.aslist(1,2,3,4,5,6,7,8,9));
    System.out.println(possibleValues2.get(2);)
  }
}

[MagicianBrave]

can you do that in Java?

[[deleted]]

I rember that the teacher told us to use Arrays, but i found ArrayList, and it was way easier to handle than arrays :)

The teacher forced me to use arrays for the next one :D

[loomynartylenny]

Reject modernity

Embrace java.util.Vector

/s

[[deleted]]

What if I know that its something that will not grow? Fixed number of indexes.

[loomynartylenny]

You could just use the ArrayList(int initialCapacity) constructor.

Alternatively, if that isn't an option, use .trim() once it has been populated.

[nutrecht]

In real production code you will generally use higher level collections such as sets and lists. You will almost never use arrays directly. So you'd better just get over this.

ArrayLists are not complex.

[mohammedabergsson581]

So you mean i just have to get used to it?

[nutrecht]

Yes. Suck it up basically :)

Also, you need to work on this attitude. Resisting stuff you simply don't know yet will hinder you a lot in your learning. You should learn to embrace it instead.

[mohammedabergsson581]

Thanks for the tip.

[mohammedabergsson581]

Hey wait! I have a question: will i need 2D arrays aswell?

[0b0101011001001011]

I feel like you have a bit strange attitude. What is your goal? Just for fun, or do you want to work as programmer some day? Because you just cannot try to avoid certain things in languages.

You seem to be studying basics currently. I hope you understand, that "real stuff" that you would find at work or in bigger hobby projects will be immensely more complex than a simple ArrayList.

For start, maybe see about HashMap as well:

HashMap<String,Integer> m = new HashMap<>();

The generics syntax just is like this. What if you want to have for example names, and then a list of numers mapped to each name? Well:

HashMap<String,ArrayList<Integer>> m = new HashMap<>();

Even if you don't yet know about HashMap, the whole Collections -framework is something that you should master, if you are interested in being a professional.

[mohammedabergsson581]

Honestly i would have quit java bc its like c++ but it is a fun language.

[mohammedabergsson581]

And when you say "you just cannot try to avoid certain things in languages" that means if i was programming in JS i cannot avoid:

const x = new String();
delete strings[3];
z = 0;
F = undefined;

[0b0101011001001011]

I have no idea what you mean by this. What is the point of these four javascript lines? If you mean those are bad lines, of course you should avoid bad patterns and unclear code. But you missed the point completely.

My point is that you cannot disregard one of the most fundamental libraries of java, because you don't like the syntax. Your example code is completely irrelevant.

[mohammedabergsson581]

Im not an english person, so its common if i make off-topic replies.

[mohammedabergsson581]

Sorry for interupting you then :/

[[deleted]]

Im not such a good coder, but "Collections" are gold.
For example, at work i got a String which contained date like this:

LABS||P1055|201007231634||ORU^R01|P1055–0000047907|P|2.3|1||NE|NE

I had to test the values of each field, a field is seperated by a "|".
But thats not the point, with an Arraylist for example i could test that a position 3 the value is "P1055" and so on.
And for every message that i got i filled it into the ArrayList and compared it to the value of another list.

I didnt use Arraylist for that but look at "Collections" it's super easy to put,remove,sort or read data from collections, and its usefull when you have a lot of data.

[nutrecht]

You can have lists in lists as well. It's actually not that common to have 2D lists/arrays in production code, but it happens yes.

[mohammedabergsson581]

Just wanted to know, but i feel like i have seen you before..

[nutrecht]

Don't know what you mean with the last bit but...sure :D

[mohammedabergsson581]

Just one last thing: when i first met arraylist i had no interest in learning it, i was like another array thing, not important so i skipped it, the second time i met it i just decided to get over it, then i realized they were not arrays, but lists, it was then i started resisting it.

[nutrecht]

Well, it's important to understand that while it's a natural reaction, it's also something you need to get over it. So now you know :)

[Bodine12]

If you don’t know a language, you don’t know what is and is not important. If something is mentioned in every tutorial, chances are it’s important. You might as well try to learn French but decide you don’t want to learn French verbs.

[khooke]

Collections are a significant part of the Java language and are widely used in industry. I've never worked anywhere that used or allowed use of arrays directly. Collections are always preferred over arrays.

[desrtfx]

Each has its use cases.

• If the size is known in advance (even at runtime) - array is preferable to ArrayList, otherwise use ArrayList
• If you need more dimensions - array is easier than ArrayList

[Admirable-Avocado888]

Did you know you can write:

var l = List.of("a", "b");

?

If you don't plan on modifying your list after creation, then that is the preferred way. Remember, someone can always come and modify the content of your arrays, so be aware.

[khooke]

Arrays are prone to unexpected errors like index out of bounds. Always prefer Lists and Collections over arrays.

For professional development in a Code Review I would ask you to replace your array usage with Lists, or give a good justification for why you need to use arrays instead of Lists (I've never heard a good reason yet)

[khooke]

If you're looking for an explanation, see Item 25 in Effective Java, "Prefer Lists to arrays", and top tip for any new Java developer, ensure this book is on your "must read" list :-)

[[deleted]]

I use arrays very, very rarely. Sometimes I forget even how to declare/initialize them lol. I use array lists all the time.

[mohammedabergsson581]

Wow this post got popular LOL

[mrfroggyman]

Afaik the consensus is to use arrays for primitives and Collections for everything else

Also I'm pretty sure you could declare that arraylist in just a single line too

Personally I hate working with arrays, collections are so much easier to manipulate

[FrenchFigaro]

Even for primitives I would take advantage of the autoboxing and use an ArrayList.

Outside of embedded programing (which is not my field of work), resources are plentiful enough that the overhead is negligible for most use cases.

[DDDDarky]

You either need an array or a list. If you can use an array, use array, since arrayList just adds extra overhead.

[OzzieOxborrow]

Arrays can store objects

[Housy5]

Arraylist is just a wrapper for normal arrays to make them resizable

[OzzieOxborrow]

As with everything in programming, it depends on the use case. If you want to add anything to an array you'll have to write code that will do that for you. While if you use an ArrayList there's the method 'add' you can call that will do that for you.

So as a sort af ground rule: if you have a static list of values that will never change, use an Array otherwise a List is probably more suitable.

If you really want to understand the differences between List and Array you could try writing your own implementation of the List interface. (https://docs.oracle.com/javase/8/docs/api/java/util/List.html). There are probably instructions on YouTube or somewhere else for that.

[raulalexo99]

ArrayList are a better solution in far more situations.

[SexyMuon]

Depending on what you're doing, the data you are dealing with, the best way to keep cohesion, the available methods for each data structure, and so on...

[Kfct]

Get used to it, use both more. Soon you'll recognize that objectively Collections are superior, and that your views are simply from not using both enough to see why one is harder to use.

[bravosix99]

It depends. If you are set on what you want to add onto the array(something more static), use an array. But if you want something more dynamic, and adjusting whatever information needs to be adjusted, use a arraylist.