How can I read and work on a textual file starting from its path in Java?

Question

I have the following task that have to be implemented in Java.

I have a String that represent the path of a txt file, something like this:

String fileFatturePa = "C:\\Users\\Andrea\\Desktop\\D150316.T1642\\myFile.txt";

This textual file contains some text (that represent XML but this is not important because I do not have to operate on it with something like XPath but I have to do simple substring operation).

So I need to read this textual file (starting from its path) and then I have to do some textual operation.

This file could be very big.

What is the best way to read it stargint from its path?

What have you done? Show some code, solve some problems. The Java API javadocs are there for your readng pleasure, and shoving "open file for reading" into a browser web search is easy. — , Jun 09 '15 at 13:58
what do you mean by working on a file? do you want to read from it or write to it — GregH, Jun 09 '15 at 14:00
possible duplicate of [Best way to read a text file](http://stackoverflow.com/questions/4716503/best-way-to-read-a-text-file) — Crembo, Jun 09 '15 at 14:00
Out of curiosity: how do you reach a reputation of 4000 ... and then come here and ask questions like a complete newbie? — GhostCat, Jun 09 '15 at 14:00
I will add that because of the nature of XML files, if you go down the path of treating this like a plain text file, and you want to make changes to it, you are going to have a bad day. Use one of the XML libraries out there to walk the elements and make your changes. — , Jun 09 '15 at 14:00

score 2 · Answer 1 · answered Jun 09 '15 at 14:06

2

A good starting point is the official Java documentation by Oracle: Basic I/O.

answered Jun 09 '15 at 14:06

Atafar

675
5
8

guy_sensei · Answer 2 · 2015-06-09T14:17:10.653

 BufferedReader reader = new BufferedReader(new FileReader(fileFatturePa));

        try
        {                           
            String line = null;         
            while ((line = reader.readLine()) != null)
            {
                  ***operations(specific to each line of the text file) ***
            }               
        }
        catch (IOException ex)
        {
            ex.printStackTrace();
        }               

        finally
        {
            reader.close();
        }

score 0 · Answer 3 · answered Jun 09 '15 at 14:03

0

Simple, you create a new File: File f = new File(path). For raed all the lines, you can use the class Fileutils from Apache Commons IO. And you will have something like: List<String> allLines=Fileutils.readlines(f)

answered Jun 09 '15 at 14:03

Nicola Bena

78
1
1
9

"This file could be very big." Now, how to solve that pesky `OutOfMemoryError` without redesigning the whole file reader... – Jun 09 '15 at 14:06
I found this article yesterday: http://www.baeldung.com/java-read-lines-large-file – Nicola Bena Jun 09 '15 at 14:10
Yes, and your example is **not** one of the "streaming" or "iterator" based approaches discussed therein. The example you give can make the heap grow unbounded as the file size grows. – Jun 09 '15 at 14:13

How can I read and work on a textual file starting from its path in Java?

3 Answers3