Java Help

[bananaman]

I have a question about Scanners in java.

I am attempting to read data from a .csv file. To do this, I am using a FileInputStream and then using a Scanner object to access the data. I have done the command useDelimeter(","); this is so that I can get each item from my database.

Unfortunately I have run into some problems while trying to take the data from the file and get it into my program. Sometimes in the .csv file there is no data between commas. So it goes like this, "Who,an,3,3,S,S,,TRUE,National,12/5/98" (Notice the ,, ).

This has made my code to generate an exception.

while (in.hasNext()) {
temp = in.next();
if (temp.charAt(0) == '"') {
do {
temp += in.next();
} while (temp.charAt(temp.length() - 1) != '"');
}

seperate.add(temp);
}

Seperate is an ArrayList<String>, in is the Scanner object, temp is a String object

When it reaches the ,, I need it to return an empty String. Why is it producing this exception and what do I need to do to get a null String instead?

[magicdanw]

I've never used scanners, but I think the String trim() method will do the job here. I forget the syntax, but you specify a delimiter, and it returns an array of Strings containing the data fields. Check the java api for the syntax, I suppose...

[bananaman]

The command String trim() will omit the leading and trailing whitespaces from a String. I think you were referring to the command String split(regex). This splits a string around the delimeter regex.

The problem with using that command is that some of my data fields contain commas in them. That is why I need to check each item as I remove it to see if it starts with a quotation mark. And as I am typing this I just realized my error. The problem is when I check the empty String. It throws an error when I try "temp.charAt(0)" because I'm checking an empty String. I will replace this with (temp.length() > 0 && temp.charAt(0)). I have to run to work right now, I will post my results this afternoon.

[magicdanw]

Yeah, when I posted that I had been awake for 29 hours straight, so I guess I wasn't thinking at my best But yes, I did mean the split command, and your realization sounds like it could fix your problem. Good luck!

[sgm]

Surely you can just use an already-written Java CSV parser?

I guarantee that there will be thousands of examples.

(CSV is a lousy format incidentally, despite its widespread usage.)

[bananaman]

I hadn't thought about using an already-written one. It is more fun to write your own anyways.

I know that CSV is not the best format, but it is the best fit for the use that I need. The normal database is stored in Access, which is much worse than CSV.

[sgm]

[bananaman]

I adjusted the code as I stated early, and now everything works fine.

[bananaman]

Maybe it is best to use a premade CSV Java utility.

While doing further coding, I kept running into unexpected behavior, so I did some testing to see what values something was holding.

Examine these two outputs and see if you can figure out the unexpected behavior.

[Weregoose]

What happens when you replace TRANS_DATE with something else?

[elfprince13]

in the future, it is ALWAYS helpful to tell *what* exception is raised. they aren't arbitrarily thrown, so the name and stack trace are always helpful to figuring out the problem.

[bananaman]

[Weregoose]

[bananaman]

That is definitely a possibility. Java typically uses a '/' as the escape character within a string. It very well could producing unexpected results.

Edit:
I tried removing the forward slashes from the .CSV file and nothing changed.

Then I tried removing the new lines from the file. That way all the data was on one line. This solved the problem entirely. I realized that the numbers 10, 11, 12, 13 were supposed to be the next entries, but since they were after a New Line instead of after a comma, they were included in the data entry before them. Because of the new line inside the String, it was overwriting number 30 on the same line. This proves why it is easier to use pre-made libraries.

[elfprince13]

[luby]

I don't see where he said he had an exception

[elfprince13]