To add commas in file

Question

Hi All,

This is my first question in this forum... I have a file with numerous data fields (both numeric and characters) in the file. I want to delimit the file with set of delimiter length like 2,5,1,9,6 etc.

(Alternatively: I have a list of field lengths such as 2,5,1,9,6, and I want to insert comma delimiters in (a copy of) the source string after each field.)

For example, if my file is like this:

9483trdcvge245621jde

then I need to insert commas at 2,5,1,9,6 etc. and the output will be:

94,83trd,c,vge245621,jde,

I need to do this in JAVA

Please help me to solve this issue. Thanks in advance

Answer 1

I think I don’t understand the question. Read the file, line by line, and insert commas into the string.

String newString = line.substring(0, firstComma) + "," + line.substring(firstComma + 1);

Of course this is terribly inefficient and can be optimized in numerous ways.

Answer 2

if (myString.equals("9483trdcvge245621jde")) {
        myString = "94,83trd,c,vge245621,jde";
    }

Jokingly ;-)

I think something like this...

private static final int[] pos = {2, 5, 1, 9, 6};
private static final String DIV = ",";

public static String parse(String str) {
 int start = 0;
 StringBuilder sb = new StringBuilder();
 for (int i = 0; i < pos.length; i++) {
  if (i > 0) { 
   sb.append(DIV);
  }
  int end = start + pos[i];
  if (end <= str.length()) {
   sb.append(str.substring(start, end));
   start = end;
  } else {
   sb.append(str.substring(start));
  }

 }
 return sb.toString();
}

Answer 3

Assuming you have all these as Strings you can use String.substring(start, end). Then simply append + the substrings and commas together.

String data = "9483trdcvge245621jde";
String result = "";

result += data.substring(0,2) + ",";
result += data.substring(2, 7) + ",";
result += data.substring(7, 8) + ",";

etc...

Note: Using + to append string like this is very slow as it reallocates and moves data around each time. There are faster ways to concatenate Strings if speed is an issue.

Answer 4

Read in the file as a StringBuilder then use something like this

StringBuilder sb = new StringBuilder(file); //The string builder
while (/*the string builder isn't finished*/)
{
  int position = ;//The position you want the comma at 2 or 4 or whatever
  sb.insert(position, ",");
}

Loop through as many times as needed.

Answer 5

String newString = "";
int[] positions = { 2, 5, 1, 9, 6 }; //etc
for (int i = 0; i > positions.length; i++) {
    String tempString = "";
    if (i == positions.length) { //for the last item
      tempString = oldString.substring(0, positions[i]);
    }
    else { //every item except the last item
      tempString = oldString.substring(0, positions[i]) + ",";
    }
    oldString = oldString.substring(positions[i]);
    newString += tempString;
}

Stored the positions in an array. Iterate through, adding the delimited strings to a new string and removing them from the old one. This might not be the best way, but its how I would do it. :P

Answer 6

I think i would do it this way

• str being the input string
• pos being the lengths of the parts after which we should put a comma

Code:

public static String partition(String str, int[] pos) {
    int oldPos = 0;
    StringBuilder builder = new StringBuilder(str.length() + pos.length);
    for(int len : pos) {
        builder.append(str.substring(oldPos, oldPos+len)).append(',');
        oldPos += len;
    }
    builder.append(str.substring(oldPos)).append(',');
    return builder.toString();
}

Answer 7

Here's one solution:

package com.foo;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class Commafy {

    public static final String SEPARATOR = ",";

    private static void fail(String message) {
        System.err.println(message);
        System.exit(1);
    }

    private static int[] argsAsInts(String[] args) {
        if (args.length < 2) {
            fail("argument list of file name followed by field lengths is required");
        }
        int[] result = new int[args.length - 1];
        for (int i = 1; i < args.length; ++i) {
            try {
                result[i - 1] = Integer.parseInt(args[i]);
            } catch (NumberFormatException nfe) {
                fail("can't convert argument \"" + args[i] + "\" to integer");
            }
        }
        return result;
    }

    private static int[] partialSums(int[] lengths) {
        int[] result = new int[lengths.length];
        int start = 0;
        for (int i = 0; i < lengths.length; ++i) {
            result[i] = start;
            start += lengths[i];
        }
        return result;
    }

    private static int[] fieldsEndAt(int[] lengths, int[] starts) {
        int[] result = new int[lengths.length];
        for (int i = 0; i < lengths.length; ++i) {
            result[i] = starts[i] + lengths[i];
        }
        return result;
    }

    private static void process(
        String fileName, int[] starts, int[] ends
    ) throws IOException {
        BufferedReader br = new BufferedReader(
            new FileReader(fileName)
        );
        final int MIN_LENGTH = ends[ends.length - 1];
        String line = br.readLine();
        while (line != null) {
            if (line.length() < MIN_LENGTH) {
                System.err.println("short input line \"" + line +"\" skipped");
            } else {
                StringBuilder sb = new StringBuilder();
                String separate = "";
                for (int i = 0; i < starts.length; ++i) {
                    sb.append(separate).append(line.substring(starts[i], ends[i]));
                    separate = SEPARATOR;
                }
                System.out.println(sb.toString());
            }
            line = br.readLine();
        }
        br.close();
    }

    public static void main(String[] args) {
        int[] lengths = argsAsInts(args);
        int[] starts = partialSums(lengths);
        int[] ends = fieldsEndAt(lengths, starts);
        try {
            process(args[0], starts, ends);
        } catch (IOException e) {
            fail("I/O Exception while processing input");
        }
    }

}

Given a data file named data/fixedlengthdata.text containing:

9483trdcvge245621jde
9483trdcvge245621jdelong
9483trdcvge245621
9483trdcvge245621jde

and run with arguments of:

data/fixedlengthdata.text 2 5 1 9 3

it produces output of:

94,83trd,c,vge245621,jde
94,83trd,c,vge245621,jde
short input line "9483trdcvge245621" skipped
94,83trd,c,vge245621,jde

(where the third line above goes to stderr, of course.)

Answer 8

This is probably the most bizzare requirement that I've ever seen, but anyway...

Psuedo-code

Collection<Integer> indexes; // initialized with indexes to add commas at 
StringBuilder bldr = new StringBuilder();

for (int i = 0; i < inString.length(); i++){

     bldr.append(inString.charAt(i));

     if (indexes.contains(i))
         bldr.append(",");

}

return bldr.toString();