Parsing Fixed-Width Files in Java

blacksnake866

This discussion will focus on the best ways to parse a fixed-width formatted file in Java. We will discuss different methods and techniques for parsing a fixed-width formatted file, such as using Java's Scanner class, using regular expressions, and using third-party libraries. We will also discuss the pros and cons of each approach, and provide examples of how to use each one. Finally, we will discuss best practices for dealing with errors and exceptions when parsing fixed-width formatted files.

Avreliy_strokach

Parsing a fixed-width formatted file in Java can be done in a few different ways. Here are the best methods for parsing such a file:

Using Scanner Class: The Scanner class is part of the java.util package, and provides several methods to parse fixed-width formatted files in Java. This method is easy to use, and will allow you to set the widths of each “column” in the file. This method is also useful if your file contains tabular data as it will allow you to parse it into columns and rows.
Using Regex: Regular expressions can be used to parse a fixed-width formatted file in Java. If you understand regex, this method is viable but might not be the best method to use.
Using Java 8 Stream: Java 8 stream API is a convenient and easy way to parse a fixed-width formatted file in Java, and is a good option if you are using modern Java.
Using OpenCSV: OpenCSV is an open-source library designed to read and write CSV, and also supports fixed-width files. You can use OpenCSV to parse your file into objects, making it easy to work with.

No matter the method you choose, parsing a fixed-width formatted file in Java is quite simple. For more details and tutorials on the various approaches, see the following links:

Coverage151

There are several ways of parsing a fixed width formatted file in Java. The best approach might depend on the particular application and context.

BufferedReader/FileReader + String.substring(int): This approach works by using a BufferedReader/FileReader to read the file one line at a time, and then using the String.substring(int) function to extract the required portions of the String. This is the simplest and most straightforward approach.
Construct Regular Expressions: This approach works by constructing a Regular Expression for each field in the file. The expressions can then be used to split the line into the required fields.
Use Apache Commons CSV: Apache Commons CSV provides classes for fixed width parsing based on the 'columnstart' and 'columnend' properties which define the start and end indices of the field data.
Use External Library: There are also a number of external libraries available, such as Flatpack and FlatWorm, which can be used to parse fixed width files.