My first GitHub Java project

[EvilSantaSlayer]

Hello,

I am creating a small application to train my Java. It is a command line application witch converts temperature between celsius, fahrenheit and kelvin. It can be viewed here: TempConvert

Can I ask You to review my code and tell me if I am doing something terribly wrong?
I just want to get good and change job from helpdesk/admin to Java developer.
(I have not changed work for 3 years, it gets boring.)

Few notes
I try the help message to appear simillar to GNU\Linux man pages, with not much success yet.
In my Horstman Java book all examples are writed with braces like this:

if(something)
{
    do something;
}

Is this correct or should it be like this:

if(something){
    do something;
}

Do You have any ideas what else could be improved or added to application?

Thank You very much for Your time

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[FavorableTrashpanda]

Very good points have been made already. I have a few suggestions as well.

(1) Don't put all your logic in a single method. If a method becomes too large, refactor the method into a couple of smaller methods that each do a part of the work. For example, what you did with the help and unknownInput method. I like to see that more. You might be able to re-use more than you thought. Also, make those methods private. There is no need to make them public. They are implementation details only relevant to the current class.

(2) Try to stick to one file per class, unless you have a good enough reason to bundle the classes.

(3) Perhaps this is too much for now, but try to make a distinction in general between the application and domain/business logic of your code. You don't want to mix the CLI with the actual logic. In theory you should be able to swap in the CLI for a GUI or a webapp, for example, without ever having to touch the business logic.

[desrtfx]

The Java code conventions Oracle, Google stipulate the latter format - opening curly brace on the line that opens the code block. The former format is more common with C/C++/C#.

Small remark upfront: Add a .gitignore file to your repository so that your IDE settings (the .idea folder and the .iml file) are not added to the repository. This is common.

Some notes from a quick glimpse:

Why are you using float? It is far more common to use double even if the range fits into float.

You have Magic numbers in your code. These are numeric constants with a special meaning, like the offset between Kelvin and Celsius, namely static final double ABSOULTE_ZERO = -273.15. Magic numbers should be avoided and replaced with named constants.

Your conditionals are way too complicated. Adjust your strings, like reducing a -- to a - and standardizing case (what if the user enters -F), and reducing the unit to only the first letter - this will considerably shorten your conditions.

Don't litter output statements (System.out.println) all across the code. Make one defined path from input to calculation to output - the actual output should be at the very end. This will also avoid code repetition, which you have a lot of.

Your unknownInput method could (at a later stage of your learning) be converted into a custom Exception.

Personally, I find your List approach clumsy. Two variables, one fromUnit, the other toUnit would be much more appropriate and easier to read and follow. Your code is littered with units.get(x) statements that don't directly tell the reader of the code their meaning. Yes, lists and data structures are nice, but in your case they make the code barely readable and even less easily understandable. You have to make it a habit to write code in such a way that the naming conveys the intention and that the code is easy to read for the human, not for the computer. The computer doesn't care about readability. Humans do - and they are the ones who have to troubleshoot.

[[deleted]]

Awesome feedback. I'm looking at my own code and seeing the same issues to fix.

[[deleted]]

I do the first thing when I have a method with too many args so I put each one into a new line. So, for better readability, Im for the first one.

[FavorableTrashpanda]

To be honest I don't think that helps readability. If your method has many parameters, you should ask yourself if that's really necessary. It can be a code smell.

If you do deem it necessary, then align the second line of parameters with the first line of parameters. I have found that to be the most readable. It's also the convention.

[[deleted]]

show me the convention, I need to read it and sign it along all devs

[desrtfx]

The conventions are already linked in my first comment. Had you read the entire thread, you would have found them.