• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 451
  • Last Modified:

readLine and goto a position

Hi

I'm kinda new to java, i'm hoping there is a simple answer to this:

I've created in java the following,

read textfile (using the method readLine),
once each line is read in, I was wondering if I could go to a specific position in the string (i.e. char 15 and 16) and only dealing with these.  If it helps a single line is as follows: " adtfg,678,dfg,62,yud,dud " so in that line I only want to deal with the 62.
I was hoping i could treat the line as an array and just skip to the number 62 but it keeps causing errors when I try to do this. And saving this value (62) as an int.

Hope that makes sense, thankyou for reading hope someone can help.
0
ncoo
Asked:
ncoo
  • 10
  • 7
  • 2
  • +2
1 Solution
 
objectsCommented:
// read line
String s = in.readLine();
// only want string from postition 15
s = s.substring(15);

0
 
CEHJCommented:
You can use

line = line.substring(line.indexOf("62"));

or

line = line.substring(14);
0
 
fave_17Commented:
String s = in.readLine();
s = s.substring(15,16);
int i = Integer.parseInt(s);
0
Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
CEHJCommented:
int i = Integer.parseInt(line.substring(14, 16));
0
 
objectsCommented:
StringTokenizer and split() are other possible options.

String tokens[] = line.split(",");
int i = Integer.parseInt(tokens[3]);

or

StringTokenizer st = new StringTokenizer(line, ",");
st.nextToken();
st.nextToken();
st.nextToken();
int i = Integer.parseInt(st.nextToken());
0
 
objectsCommented:
> int i = Integer.parseInt(line.substring(14, 16));

gee, thats original :D
0
 
CEHJCommented:
>>gee, thats original :D

Quite correct - it's original in the sense that so far i am the only one to have posted the correct string indexes
0
 
objectsCommented:
That code was already posted, if you have a clarification to make about it then state what that clarification is.
Posting a duplicate line of code just confuses the thread.

And the line in the question is just an example so the actual index values are not really relevant anyways.
0
 
CEHJCommented:
>>That code was already posted...

It's much clearer to post working code than to enter into explanations

>>...so the actual index values are not really relevant anyways

LOL
0
 
objectsCommented:
> It's much clearer to post working code than to enter into explanations

You're kidding right.
0
 
CEHJCommented:
What's more, the last time i pointed out inaccuracies in someone's code, i got accused of 'critisism':

http://www.experts-exchange.com:8080/Programming/Programming_Languages/Java/Q_20926569.html
0
 
objectsCommented:
ncoo,

If you're lines have a fixed format, ie. the value you need to extract is always at the same position in the line then you can use the technique suggested by fave_17 to extract the value.
If the lines are not fixed, and the column position may vary then you will need to tokenise the string using split() or StringTokenizer.
0
 
CEHJCommented:
Either way, this will allow you to access the retrieved numbers as an array:

      public int[] getNumbers(String fileName) {
            BufferedReader r = null;
            List numbers = new ArrayList();
            try {
                  r = new BufferedReader(new FileReader(fileName));
                  StreamTokenizer tok = new StreamTokenizer(r);
                  while (tok.nextToken() != tok.TT_EOF) {
                        if (tok.ttype == tok.TT_NUMBER) {
                              numbers.add(new Integer((int)tok.nval));
                        }
                  }
                  int[] result = new int[numbers.size()];
                  for(int i = 0;i < result.length;i++) {
                        result[i] = ((Integer)numbers.get(i)).intValue();
                  }
                  r.close();
                  return result;
            }
            catch (IOException e) {
                  e.printStackTrace();
                  return null;
            }
      }
0
 
objectsCommented:
> this will allow you to access the retrieved numbers as an array

Must have missed that requirement in the question :)
0
 
ncooAuthor Commented:
CEHJ,

That is the prefered way of doing it through arrays, since the length of the desired number i want can sometimes be one digit (eg adtfg,678,dfg,6,yud,dud in this case i require 6) I'm just having some difficulty setting up the code you've supplied.

When I try to run it I just get "illegal start of expression".  Can you just make it so it prints each array to the screen one by one, because then I'll be able to see what's going on better and addapt it more easily, since I haven't come accross the class Token before and not totally sure what it does.

Thanks Everyone,
0
 
objectsCommented:
> That is the prefered way of doing it through arrays

Is it??

> since the length of the desired number i want can sometimes be one digit

Both example code I posted above handles this.

String tokens[] = line.split(",");
int i = Integer.parseInt(tokens[3]);

or

StringTokenizer st = new StringTokenizer(line, ",");
st.nextToken();
st.nextToken();
st.nextToken();
int i = Integer.parseInt(st.nextToken());

They just show how to extract one int field as you mentioned in your question, but if you needed more it would be a simple modification.

String tokens[] = line.split(",");
int[] no = new int[] ( Integer.parseInt(tokens[1]), Integer.parseInt(tokens[3]) };
0
 
objectsCommented:
if you want an array containing values for each lines then simply add each value to a List


String tokens[] = line.split(",");
values.add(tokens[3]);
0
 
ncooAuthor Commented:
Thanks Objects, that does exactly what i wanted.

It looks so simple though, to work it all out.
0
 
objectsCommented:
0
 
krakatoaCommented:
Grade B - ROTFL! :))
0
 
CEHJCommented:
>>That is the prefered way of doing it through arrays

Yes, it certainly is convenient to have the numbers in an array

>>When I try to run it I just get "illegal start of expression".  

Probably because you put it in the wrong place
0

Featured Post

Concerto's Cloud Advisory Services

Want to avoid the missteps to gaining all the benefits of the cloud? Learn more about the different assessment options from our Cloud Advisory team.

  • 10
  • 7
  • 2
  • +2
Tackle projects and never again get stuck behind a technical roadblock.
Join Now