Duplicate Finder Between 2 Very Large Files

Problem Statement

Let's assume we have two files, each containing a list of numbers, one number per line.

The assignment is to write a function which takes these two files and finds all the numbers that are only present in both files.

For this exercise, make the following assumptions:

Numbers are 64 bits integers
The files are very large, so that neither of them fits entirely in memory
The numbers are not stored in any particular order, and they may contain duplicates within the same file
The output should be written to another file, in the same format.

Import Maven Dependencies. Run main function in FindDuplicates class.
The program uses BufferedReader and BufferedWriter to read and write one line at a time from the large files.
As the first step, the program by default generates 2 files each with 5e7 random numbers between 9_000_000_000_000_000_000L and 9_000_000_000_090_000_000L. The number of numbers and the maximum number and minimum number generated can be changed in the Util class. The files are generated in /files/input/ and are named as file1.txt and file2.txt .
The program assumes 128MB of memory available for sorting purposes. The amount of memory that can be used by the program can also be changed from Util class.
The program creates chunks of each file and sorts them separately. These are stored in /files/sortedInputFiles/sortedChunks/. The number of chunks depends upon the size of the generated files and the amount of memory available for sorting.
In the next step, the chunks for one file are merged using a heap. The algorithm is same as merging K sorted lists. Duplicate numbers in the file are also removed and the output is stored in /files/sortedInputFiles/sortedOutput/. The ouput is stored in single file.
The program finally finds duplicates in file1 and file2 using the merge step of merge sort and stores it in /files/duplicates/duplicates.txt