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

Question

Can someone help me to read a selective column of data in a text file into a list..

e.g.: if the text file data is as follows

-------------
id name age
01 ron   21
02 harry 12
03 tom   23
04 jerry 25
-------------

from the above data if I need to gather the column "name" using list in java and print it..

Answer 1

java.util.Scanner could be used to read the file, discarding the unwanted columns. Either print the wanted column values as the file is processed or add() them to a java.util.ArrayList and print them once processing is complete.

A small example with limited error checking:

Scanner s = new Scanner(new File("input.txt"));
List<String> names = new ArrayList<String>();

// Skip column headings.

// Read each line, ensuring correct format.
while (s.hasNext())
{
    s.nextInt();         // read and skip 'id'
    names.add(s.next()); // read and store 'name'
    s.nextInt();         // read and skip 'age'
}

for (String name: names)
{
    System.out.println(name);
}

Answer 2

Use a file reader and read it line by line, break on the spaces and add any column you want to the List. Use a BufferedReader to grab the lines by something like this:

BufferedReader br = new BufferedReader(new FileReader("C:\\readFile.txt"));

Then you can do to grab a line:

String line = br.readLine();

Finally you can split the string into an array by column by doing this:

String[] columns = line.split(" ");

Then you can access the columns and add them into the list depending on if you want column 0, 1, or 2.