Why am I getting the following error on compilation: "cannot find symbol - method toArray()" (java)?

Question

Here's the relevant lines of code:

HashSet<Integer> products = new HashSet<Integer>();  
...  
Integer[] arrProducts = prodDigs.toArray();`

Any idea why I'm getting the error stated in the question?

I'm using BlueJ as my IDE if it's at all relevant.

this code is not enough to identify the issue. proDigs may not be created on it may not visible to your code block — Sasikumar Murugesan, Jun 06 '18 at 05:20
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Yes, it was a typo. It should indeed have been `products.toArray()`. As for prodDigs, it's an int[] and should not be referred to in this line. Lesson learned: don't write code after midnight. — Thomas Riley, Jun 06 '18 at 17:14

score 1 · Answer 1 · answered Jun 06 '18 at 05:28

1

With your little decription, I could guess you want to convert hash set to array using to Array():

To convert your hash set to integer array you can use :

Integer[] arrProducts = products.toArray(new Integer[products.size()]);

answered Jun 06 '18 at 05:28

Adya

It would be nice to explain, first the typo, then why you use `AbstractCollection.toArray(T[])` instead of `AbstractCollection.toArray()`. – AxelH Jun 06 '18 at 05:35
Ah, found the typo - that's not in my code, that's a result of being a first-time poster on Stack Overflow, and as such, messing up the formatting @AxelH – Thomas Riley Jun 06 '18 at 13:49
Although yes, I would like an explanation as to why use toArray(T[]) instead of toArray(). I think I've figured it out after reading the documentation now that I know that you should do that in my case (it's because I've instantiated my HashSet, isn't it?) – Thomas Riley Jun 06 '18 at 13:53
@AxelH found the typo, and I can't make an edit to my comment yet, but must leave for class before I'll be able to. That's why you shouldn't code at 1 AM. – Thomas Riley Jun 06 '18 at 14:00
Don't worry @ThomasRiley , those remarks were addressed to Adya to improve the answer. Not a remark on your code ;) – AxelH Jun 06 '18 at 14:01

score 0 · Answer 2 · answered Jun 06 '18 at 05:53

0

Just try Java 8 Way

Option 1

Integer arrProducts[]=products.stream().toArray(Integer[]::new);

Option 2

Integer arrProducts[]=products.stream().toArray(n->new Integer[n]);

answered Jun 06 '18 at 05:53

Juhan

1

Would you mind offering an explanation of why this works? I read the stream() method on the documentation for java.util.Collection, but am having trouble figuring out exactly what it does. – Thomas Riley Jun 06 '18 at 13:54

2 Answers2