In this module, you will learn about the basics of cryptography, the science of keeping information private and secure. You will learn about simpler cryptographic systems, which were used from the Roman Empire through the early 1900s. You will learn how to implement these ciphers, as well as how to break them. To solve these problems, you will work more with processing Strings, but also learn about arrays—a way to store an indexable sequence of elements. You will be able to: (1) combine Strings using concatenation; (2) build Strings within a Java program using StringBuilder; (3) use arrays to store and manipulate collections of data; (4) refactor your programs for improved organization using object-oriented principles; (5) and practice effective algorithm design.

After completing this module, you will be able (1) to program a word frequency counter to analyze any input text file, (2) to select and substitute words from a list into a document template using both ArrayList and HashMap, (3) to create new lists to use in templates, (4) to recognize brittle code, and (5) to improve code with flexible, object-oriented design. You will gain these skills in the framework of developing a randomly generated story that we call GladLibs. You may discover that bald lions change peoples’ lives, or that fluffy dinosaurs get things done in a jiffy. We hope you have fun developing your Java skills this week!

In this module, you will learn about how web server logs store information about visitors to a website, and you will write programs to access information like user IP address, date and time of access, and more. Using Java programs you write in this module, you will be able (1) to read information from a web server log, (2) to count the number of unique visitors to your website, and (3) to count the number of times each visitor uses your website.

In this module, you will develop a program to break the Vigenère Cipher, a more complex version of the Caesar Cipher. You will improve your program in three stages: first decrypting messages where you know the language and key length, then adding the capability to handle messages with unknown key length, then extending the program to handle messages in a range of possible languages. Through this project, you will be able (1) to effectively use HashSet and HashMap, (2) to expand an algorithm from solving a simpler problem to handle broader, more complex problems, and (3) to design and modify program code involving a more complex collection of classes, methods, and data.