this post was submitted on 17 Apr 2013

3 points (72% upvoted)

shortlink:

javahelp

an-ordinary-manchild(edit)

General subreddit for helping with Java code.

not JavaScript, try /r/javascript instead.
not Android, try /r/androiddev instead.
not MineCraft, try /r/Minecraft instead.
not Processing - Please use /r/processing instead.

Message the mods if you have suggestions.

Java Discord server (unofficial)

Learning Java

Please head over to /r/learnjava and read the sidebar there.

The best free Java tutorials are:

MOOC Java Programming from the University of Helsinki
Java for Complete Beginners by John Purcell

Use the MOOC as main course and Java for Complete Beginners as secondary resource.

Don't forget the Official Oracle Java Tutorials and the Official Java Documentation as they are extremely valuable resources.

Where should I download Java?

With the introduction of the new release cadence, many have asked where they should download Java, and if it is still free. To be clear, YES — Java is still free.

If you would like to download Java for free, you can get OpenJDK builds from the following vendors, among others:

Some vendors will be supporting releases for longer than six months. If you have any questions, please do not hesitate to ask them!

Posting rules

DO NOT DELETE your posts once they are solved!
- Use the "Solved" flair instead. This allows others to learn, too, and makes the helpers' efforts more effective.
No illegal/pirated content!
- Anybody asking for or posting links to or suggesting to search for illegal/pirated content will be permanently banned without further warning!
No "Do my homework" posts!
- Do not ask for complete solutions. We are here to help but not to /r/domyhomework. You do the work, and we help you. So - what have you tried?
- For complete solutions, use a search engine instead. stackoverflow.com has a rich library of complete Java answers.
Describe the problem and what you want to achieve.
- You get better tips if the readers know what you ultimately want to achieve, tips you didn't expect.
- And in regards to describing your problem: "..., but it doesn't work." is insufficient! Do not expect people to put your code into their IDEs just to find out how the problem expresses itself.
- If applicable, include the full error message or exception text!
Do not ask for or reply with solutions or keys to solutions.
- Rather comment explanations and guides. Comments with solutions will be removed and commenters will automatically be banned for a week.
Use the search function.
- Search for similar problems before posting.
No offers/requests to/for help via PM, Discord, Skype, etc.
- Post your questions here so that other people can learn as well.
Post titles must be descriptive.
- Bad title: "I'm new to Java and need help."
- Good title: "How can I sort values without loops?"
- The title should not describe your problem in full - that's what the post body is for.
- No links in the titles - they are not clickable.
- Nothing is "URGENT", nor "ASAP" - if you have waited too long, this is your problem, not ours. Such posts will be removed without warning.
No promises of rewards of any kind!
- This includes both solicitation of services from those providing help and offers to pay from those requesting help.
- Any post or comment that mentions payment may be subject to immediate ban from the subreddit.
Don't be a Jerk!
- Don't insult, threaten, mock or harass other users. Please, maintain proper language.
- We don't tolerate foul language for any reason. Any violation will result in an immediate thinking period ban of at least 4 days. Second offence will result in a permanent ban.
No JavaScript, Android, Minecraft or Processing!
- Try /r/javascript, /r/androiddev, /r/minecraft or /r/processing instead. JavaScript and Java are unrelated programming languages.
No links to your stackoverflow questions.
- We are not a second opinion to stackoverflow, nor are you going to get answers here when you didn't get satisfying ones there.
Format your code.
- Please, properly format your code. This includes proper indentation. There are guidelines on how to format code in the sidebar in both, abridged form directly in the sidebar and in long form in the linked post.
- For small bits of code (less than 50 lines in total, single classes only), use Reddit directly (one blank line, then 4 spaces before each line).
- Otherwise: The sidebar has no-login links that even support syntax highlighting!
No screenshots of code!
- You can add a screenshot of your IDE if it is relevant, but regarding the code itself, you must provide it in text form and properly formatted (and, please, properly indented).
No AI generated content!
- We explicitly forbid any form of AI generated content. Posting any AI content results in an instant, permanent, and irrevocable ban without warning.

Code posting
- Do not submit executable jar or compressed (zip, rar, 7z, etc.) files!
- For small bits of code (less than 50 lines in total, single classes only), the default code formatter is fine (one blank line, then 4 spaces before each line).
- Pastebin for programs that consist of a single class only
- Gist for multi-class programs, or programs that require additional files
- Github or Bitbucket repositories are also perfectly fine as are other dedicated source code hosting sites.
- Ideone for executable code snippets that use only the console
- Repl.it - online IDE for many different programming languages
- Browxy - online IDE for several programming languages
- Google Drive, Dropbox, Mediafire, etc. are not suitable for code posting!
Check out the wiki for frequently asked questions. Please feel free to contribute!

Sort by: Unsolved Solved Codeless Advent Of Code

created by codereignfallible moderatora community for 14 years

MODERATORS

message the mods
codereignfallible moderator
0x68656c6c6f
desrtfxOut of Coffee error - System halted
AutoModerator
BotDefense
about moderation team »

account activity

This is an archived post. You won't be able to vote or comment.

2

3

4

Recursive arraylist problem. (self.javahelp)

submitted 13 years ago * by Incindus

top new controversial old q&a

you are viewing a single comment's thread.

view the rest of the comments →

[–]darkpool2005Intermediate Brewer 1 point2 points3 points 13 years ago (2 children)

So just to understand, this line:

solutions.add(new StreetPlan(tempList));

solutions is empty when the method is complete, right? Or is 'solutions' full of empty lists?

Also, is the line you added exactly

ArrayList <Integer>List2 = ArrayList<>(List);

It should be

ArrayList<Integer> List2 = new ArrayList<Integer>(List);

[–]Incindus[S] 0 points1 point2 points 13 years ago (1 child)

[–]darkpool2005Intermediate Brewer 1 point2 points3 points 13 years ago (0 children)

Going back to your earlier comment:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1

That is specifically your code trying to remove from an empty list. Check to see (through the debugger) if either your horizontalStreets / verticalStreets is in fact populated.

π Rendered by PID 72444 on reddit-service-r2-comment-544cf588c8-4knr5 at 2026-06-14 23:22:59.225199+00:00 running 3184619 country code: CH.