Btukfyl

Im writing a program to read in a file and store the strings in arraylist and ints in an array. The file contains strings and ints in the format: String int

I have already got the string section to work, I'm looking to know why the following code is populating my array with the number 7, six times rather than the correct numbers. Correct output: 12, 14, 16, 31, 42, 7 but like I said, it gives, 7, 7, 7, 7, 7, 7

Code:

BufferedReader buffy = new BufferedReader(new FileReader(fileName));

     while((str = buffy.readLine()) != null) {

        for(int i = 0; i <= arrayInt.length - 1; i++) {

           for(int k = 0; k <= str.length()-1; k++) {

              if(str.substring(k, k + 1).equals(" ")) {

                 String nums = str.substring(k+1);

                 arrayInt[i] = Integer.parseInt(nums);

              }

           }

        }

     }

     buffy.close();

I can provide the rest of the code if you need me to,but anyways, any advice or tips are appreciated. Thanks in advanced.

This happens because for each line in file you fill whole array.

Try this:

 int i = 0;

 BufferedReader buffy = new BufferedReader(new FileReader(fileName));

 while((str = buffy.readLine()) != null) {

    if(i < arrayInt.length) {

       for(int k = 0; k <= str.length()-1; k++) {

          if(str.substring(k, k + 1).equals(" ")) {

             String nums = str.substring(k+1);

             arrayInt[i] = Integer.parseInt(nums);

             break;

          }

       }

       i++;

    }

 }

 buffy.close();

Also you can use indexOf

 int i = 0;

 BufferedReader buffy = new BufferedReader(new FileReader(fileName));

 while((str = buffy.readLine()) != null) {

    if(i < arrayInt.length) {

       int k = str.indexOf(" ");

       if(k!=-1) {

          String nums = str.substring(k+1);

          arrayInt[i] = Integer.parseInt(nums);

       }

       i++;

    }

 }

 buffy.close();

File read are typically batch/ETL kind of job and if this code is going to production and would be used multiple times instead of only once then I would like to stress on Performance and Ease of Maintenance:

Only read least characters to identify the space index

• @talex added a very good line of code i.e. break; inside the loop that way you won't need to read till the end of line but this would only work if the string has no spaces. If the string can contain spaces than you would need lastIndexOf space (" ") or no break; at all.


• 
  

  I prefer using framework method lastIndexOf assuming you are using java because:

  
  
  
  
  
  1. it would start reading from right instead of left and assuming the numbers would be always less length than the string it would find index of space faster in most of the cases than reading from start.
  
  
  2. 
     

     2nd benefit is that there are lots of scenarios framework/utilities method already handled so why to reinvent the wheel

     
     
     

     int k = str.lastIndexOf(" ");

     
     
  
  

  3. last but not the least if someone else is going to maintain this code it would be easier for him/her as there would be enough documentation available.

  
  
  
  

Only read required lines from files

Seems like you only need certain number of lines to read arrayInt.length if that's the case then you should 'break;' the while loop once the counter i is more than array length.

I/O operations are costly and though you will get right output you would end-up scanning whole file even if it's not required.

Dont forget try-catch-finally

The code assumes that there will not be any issue and it would be able to close the file after done but there could be n number of combinations that can result in error resulting the application to crash and locking the file.

See the below example:

    private Integer readNumbers(String fileName) throws Exception {

        Integer arrayInt = new Integer[7];

        String str = null;

        BufferedReader buffy = new BufferedReader(new FileReader(fileName));

        try {

            int i=0;

            while ((str = buffy.readLine()) != null) {

                if(i> arrayInt.length){

                    break;

                }

                //get last index of " "

                int k = str.lastIndexOf(" ");

                if(k > -1){

                    String nums = str.substring(k+1);

                    arrayInt[i] = Integer.parseInt(nums);

                }

                //increment the line counter

                i++;

            }

        } catch (Exception ex) {

            //handle exception

        } finally {

            buffy.close();

        }

        return arrayInt;

    }