Campbell Ritchie

Ansamana Sankarray wrote:. . . my own solution  . . .

That looks good but you  should be able to use something on the lines of b = !b; to reduce lines 18‑23 to one statement.
What do lines 26‑28 mean?

Well done sorting it out )

Those print a triangle programs are always annoying.
Suggest you work out a formula. You need to work out the length of the word, and the number of spaces before and after the nth letter (number of spaces may be 0).
I suggest you write down how you would do that, which will be the beginning of writing your code. There is no point in even looking at code until you have worked out/thought through the algorithm you are using and the problem you are solving.

Moved to our Spring forum.

. . . and does your code work? What sort of output do you get? Are you suffering any exceptions?
Don't declare your List as ArrayList; declare it as List. Don't call a List arr; it isn't an array. Call it numbers or something like that.
Why have you got the bang sign/not operator in line 3? I think that shouldn't be there.
If you think about the different kinds of collection/data structure available, which you can read about here, you will find a collection type whose size() method will tell you how many distinct elements you have.

Congratulations, all four of you
And thank you JF for coming here to promote your book.

I suggest you should start by creating a search facility without a GUI.

Somebody suggested it is a CLASSPATH problem, and I am beginning to think that is correct. Please show us what happens if you write echo %CLASSPATH%

This is what I used; it is slightly different from a proper class because I used JShell.final int SIZE = 100; BitSet lamps = new BitSet(SIZE); for (int i = 0; i < SIZE; i++) {    for (int j = i + 1; j <= SIZE; j += i + 1)    {      lamps.flip(j - 1);   } } for (int i = 0; i < SIZE; i++) {   if (lamps.get(i))   {      System.out.printf("%3d", i + 1);   } }output:-
1  4  9 16 25 36 49 64 81100
I used + 1 in line 5 otherwise I'd have been adding 0 and gone into an infinite loop.
Now, knowing what we know about count of factors: why does this method create that particular series of numbers?

Chas Blessed wrote:. . . I never meta language I didn't like"? . . . .

Hahahahahahahahaha!

Welcome to the Ranch

Welcome to the Ranch

Is this code from Head First Java by Sierra and Bates? Did you copy it form the book or download it from the book's website? The code from the website is subtly different, in that it has package declarations for each class.

That's a different method from what I tried. I like the counting of factors.

What would you do for these numbers?
[-10,4,8,-11,0,10,12,-2]

Jay Rex wrote:. . .

That technique of creating objects is error-prone

How would I do that in a better way?

If you are reading from a text file, you are stuck with that technique. You have the awkward task of ensuring that the format of the file and the way you are reading it match. You are now coupled to the format of the file, and I think that is unavoidable.
There is another way to read things: read a whole line with your Scanner and divide it into an array with String#split; you can probably use ";" as the regex. Please check, but I think the semicolon isn't a meta‑character.

I see you are up to date with try-with-resources

Thanks to you

Gee, shucks, you got me all 'barrassed!

. . . . Are documentation comments seen in a different light?

Yes. You use the javadoc tool to create an HTML document which you open with a web browser, and you use the documentation comments to guide you about how to use the code.

. . . Where do I create the static method, inside Test.java or Product.java? Is one more correct than the other? . . .

If you use a factory method to create an object of a class, it is usual to put that method in the same class. So Product in this case.

. . . What would be a better name for Test.java?

There isn't a really good name for that sort of class, but how about ProductDemo?