This is an example of 3 different ways to use Java to process big data files. One file is the Java's bufferedReader() method, the second is with Java's fileInputString() method, and the third way is with the help of the Apache Commons IO package, lineIterator().

There is also use of Java's date time methods Instant.now() and Duration.between() to determine the performance of the 3 different implementations, and which is most efficient processing the files.

Download the large file zip here: https://www.fec.gov/files/bulk-downloads/2018/indiv18.zip

The main file in the zip: itcont.txt. I used the smaller file included in the config folder test.txt to test before running my solutions against the larger scale files.

I used Intellij's handy Spring Boot configurations to create main class runners for each of the three main files I included inside the repo for the purposes of this example.

Add the file path for one of the files (could be the big one itcont.txt or any of its smaller siblings in the indiv18 folder that were just downloaded - you can see how I set up my relative and hard coded file paths in each of the files), and then run whichever main class file you want by right clicking the file and selecting 'Run'. Intellij Run

Either run ./gradlew assemble and then

• java -cp ./build/libs/readFileJava-0.0.1-SNAPSHOT.jar com.example.readFile.readFileJava.ReadFileJavaApplicationBufferedReader [path-to-file],
• java -cp ./build/libs/readFileJava-0.0.1-SNAPSHOT.jar com.example.readFile.readFileJava.ReadFileJavaApplicationFileInputStream [path-to-file],
• java -cp ./build/libs/readFileJava-0.0.1-SNAPSHOT.jar com.example.readFile.readFileJava.ReadFileJavaApplicationLineIterator [path-to-file]
• java -cp ./build/libs/readFileJava-0.0.1-SNAPSHOT.jar com.example.readFile.readFileJava.ReadFileJavaApplicationStoringOnlySummaryData [path-to-file] for whichever method you want to run, from the command line.

If path-to-file is omitted, the smaller test file will be used instead.

Or the easier way:

You can set up the Spring Boot runner in Intellij, by simply specifying which main class file you want to run. Intellij Configuration

Then you'll see the answers required from the file printed out to the terminal.

Performance testing is already implemented for all three files as well using Instant.now(). You can see the performance for the three methods by passing files of different sizes and seeing how long it takes to process them.

The downloadable file seems to be live data that keeps getting larger. When I downloaded the file in the beginning of Oct 2018, it was 2.55GB. Now, some users have reported it being 3.5GB large, so please be aware some of your results and numbers will differ from mine for that reason.

Thanks to AtomicStryker for his contribution to this repo. He added the FileReadingChallenge.java file, which demonstrates an asynchronous way of using fibers from the CompletableFuture API to read the file even faster. I appreciate the addition to provide even more ways to quickly churn through large amounts of data in small amounts of time.

Thanks also to Morgen Peschke for his excellent contribution to the repo. He added the ReadFileJavaApplicationStoringOnlySummaryData.java file. It demonstrates another, more efficient solution using different data structures to solve the problems. Full details of his thought process and implementation of the code can be read here.