How should I parse this simple text file in Java?

Question

I have a text file that looks like this:

grn129          agri-
ac-214          ahss
hud114          ahss
lov1150         ahss
lov1160         ahss
lov1170         ahss
lov1210         ahss

What is the best way to parse this file using Java if I want to create a HashMap with the first column as the key and the second column as the value.

Should I use the Scanner class? Try to read in the whole file as a string and split it?

What is the best way?

Answer 1

Here's how I would do it! I'm almost exclusively a Java programmer since 2000, so it might be a little old fashioned. There is one line in particular I'm a little proud of:

new InputStreamReader(fin, "UTF-8");

http://www.joelonsoftware.com/articles/Unicode.html

Enjoy!

import java.io.*;
import java.util.*;

public class StackOverflow2565230 {

  public static void main(String[] args) throws Exception {
    Map<String, String> m = new LinkedHashMap<String, String>();
    FileInputStream fin = null;
    InputStreamReader isr = null;
    BufferedReader br = null;
    try {
      fin = new FileInputStream(args[0]);
      isr = new InputStreamReader(fin, "UTF-8");
      br = new BufferedReader(isr);
      String line = br.readLine();
      while (line != null) {
        // Regex to scan for 1 or more whitespace characters
        String[] toks = line.split("\\s+");
        m.put(toks[0], toks[1]);
        line = br.readLine();
      }
    } finally {
      if (br != null)  { br.close();  }
      if (isr != null) { isr.close(); }
      if (fin != null) { fin.close(); }
    }

    System.out.println(m);
  }

}

And here's the output:

julius@flower:~$ javac StackOverflow2565230.java 
julius@flower:~$ java -cp .  StackOverflow2565230  file.txt 
{grn129=agri-, ac-214=ahss, hud114=ahss, lov1150=ahss, lov1160=ahss, lov1170=ahss, lov1210=ahss}

Yes, my computer's name is Flower. Named after the skunk from Bambi.

One final note: because close() can throw an IOException, this is how I would really close the streams:

} finally {
  try {
    if (br != null) br.close();
  } finally {
    try {
      if (isr != null) isr.close();
    } finally {
      if (fin != null) fin.close();
    }
  }
}