extract data column-wise from text file using Java

Question

I'm working under Java and want to extract data according to column from a text file.
"myfile.txt" contents:

    ID     SALARY RANK  
    065    12000   1
    023    15000   2
    035    25000   3
    076    40000   4

I want to extract the data individually according to any Column i.e ID, SALARY, RANK etc
Basically I want to perform operations on individual data according to columns.

I've listed the data from "myfile.txt" by using while loop and reading line-by-line:

    while((line = b.readLine()) != null) {
          stringBuff.append(line + "\n");
       }

link: Reading selective column data from a text file into a list in Java

Under bove link it is written to use the following: String[] columns = line.split(" ");

But how to use it correctly, please any hint or help?

mrcaramori · Accepted Answer · 2013-06-11 13:23:06Z

4

You can use a regex to detect longer spaces, example:

String text = "ID     SALARY RANK\n" +  
            "065    12000   1\n" +
            "023    15000   2\n" +
            "035    25000   3\n" +
            "076    40000   4\n";

Scanner scanner = new Scanner(text);

//reading the first line, always have header
//I suppose
String nextLine = scanner.nextLine();
//regex to break on any ammount of spaces
String regex = "(\\s)+";


String[] header = nextLine.split(regex);

//this is printing all columns, you can 
//access each column from row using the array
//indexes, example header[0], header[1], header[2]...
System.out.println(Arrays.toString(header));

//reading the rows
while (scanner.hasNext()) {
    String[] row = scanner.nextLine().split(regex);

    //this is printing all columns, you can 
    //access each column from row using the array
    //indexes, example row[0], row[1], row[2]...
    System.out.println(Arrays.toString(row));
    System.out.println(row[0]);//first column (ID)
}

edited Jun 11, 2013 at 13:23

answered Jun 10, 2013 at 17:48

mrcaramori

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3 Comments

Aman Chawla Over a year ago

It is printing the whole text file...I want each column's access individually

Aman Chawla Over a year ago

ok, but how to print row 1 i.e row[1] to be used where? System.out.println(Arrays.toString(row[1])); shows an error, how to use them???

mrcaramori Over a year ago

Arrays.toString() is to show an array, row[1] is a String, so it doesn't work, you would have to change that. Edited the answer, take a look.

Majid Laissi · Accepted Answer · 2013-06-10 17:44:44Z

3

   while((line = b.readLine()) != null) {
      String[] columns = line.split(" ");
      System.out.println("my first column : "+ columns[0] );
      System.out.println("my second column : "+ columns[1] );
      System.out.println("my third column : "+ columns[2] );
   }

Now instead of System.out.println, do whatever you want with your columns.

But I think your columns are separated by tabs so you might want to use split("\t") instead.

answered Jun 10, 2013 at 17:44

Majid Laissi

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1 Comment

0x6C38 Over a year ago

in his case " " isn't the separator

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