Java-MiniProjects

This repository contains several mini-projects using Java programming language that have been completed to gain practice and skill training.

Cryptography

This mini-project is about the basics of cryptography, the science of keeping information private and secure. It contains cryptographic systems, which were used from the Roman Empire through the early 1900s, like Caesar Cipher and Vigenère Cipher (a more complex version of the Caesar Cipher). These ciphers have been implemented, also created an algorithm for breaking them. Skills gained:

• combine Strings using concatenation and build Strings using StringBuilder;
• effectively use HashSet and HashMap;
• use arrays (and some other collections like HashMap, HashSet, ArrayList) to store and manipulate collections of data;
• expand an algorithm from solving a simpler problem to handle broader, more complex problems;
• design and modify program code involving a more complex collection of classes, methods and data;
• refactor programs for improved organization using object-oriented principles;
• and practice effective algorithm design.

Project Structure

This project consists of two packages in which the logic of the following decisions is implemented:

• Caesar Cipher encryption and decryption (with 1 and 2 keys), Caesar Cipher breaker (1 and 2 keys) and some others helpful methods & classes which helps to encrypt or decrypt message (like word lengths counter or index of max finder);
• Vigenère Cipher (encryption/decryption), Vigenère breaker, and other helpful methods. The principle of this cipher is based as a sequence of Caesar ciphers with different shift values, so it uses Caesar Cipher class implementation (for simplicity, clarity and understanding how this algorithm works it uses a new slightly extended class for this).
• Test cases implemented with JUnit
• The project structure is fully consistent with the Maven standart directory layout, the project was generated using maven quickstart archetype with resources folder.

The project was implemented and slightly changed (somewhere the code was optimized, somewhere the project structure was changed, somewhere unnecessary classes were removed with a non-optimal implementation of the algorithm, created for educational and demonstration purposes, and somewhere test cases were optimally implemented) thanks to the Coursera course Java Programming: Arrays, Lists, and Structured Data from Duke University.

Telling Random Stories from Templates

This mini-project is about a randomly generated story from templates. For example, the result could be something like a story about bald lions that change people's lives, or that fluffy dinosaurs get things done in a jiffy. Skills gained:

• program a word frequency counter to analyze any input text file;
• select and substitute words from a list into a document template using both ArrayList and HashMap;
• create new lists to use in templates;
• recognize brittle code;
• improve code with flexible, object-oriented design.

Web Server Logs

This mini-project is about how web server logs store information about visitors to a website and how to access information like user IP address, date and time of access, and more.

Skills gained:

• read information from a web server log;
• count the number of unique visitors to the website;
• count the number of times each visitor uses the website.