For this project you will be writing a java program with methods for encrypting and decrypting text.

Credits: This project was taken from Microsoft MOOC: Learn to program in Java.

Note: Please implement your own library methods and use them for this assignment. Don't use pre Existing library methods.

Part 1 - Normalize Text

The first thing we will do is normalize the input message so that its easier to work with.

Write a method called normalizeText which does the following:

Removes all the spaces from your text

Remove any punctuation (. , : ; ! ? ( ) )

Turn all lower-case letters into upper-case letters

Return the result.

The call

normalizeText(This is some eally\ great. (Text)!?) 

should return

THISISSOMEREALLYGREATTEXT 

Part 2 - Obfuscation

Well be turning out text into Obish, a language game designed to let people who know the rules talk to each other privately (sort of like Pig Latin but less well-known). The rules for Obish are simple: you simply insert the syllable ob in front of every vowel sound. So mister ackerman becomes mobistober obackobermoban. With a little practice you can learn to speak this with your friends when you need to hide a conversation from outsiders. This part isnt really encryption, but it does make your message a little harder for people who arent in the know to understand.

Write a method called obify that takes a String parameter (the message to be obfuscated) and returns a string in which every vowel (A, E, I, O, U, Y) is preceded by the letters OB (be sure to use capital letters).

If we call obify on THISISSOMEREALLYGREATTEXT, it should return

THOBISOBISSOBOMOBEROBEOBALLOBYGROBEOBATTOBEXT 

Note: In spoken Obish, you normally wouldnt put an ob in front of the double vowel sound EA in GREAT, but we want to keep our program simple so well insert OB in front of both vowels.

Part 3 - Unobfuscation

Write a method called unobify that takes a string in Obish and returns the string in the original language. So if you call:

String plainText = unobify(OBI LOBIKOBE CHOBEOBESOBE); 

then plainText would store I LIKE CHEESE.

Part 4 - Caesar Cipher

Next well be writing a Caesar Cipher. The Caesar cipher is just about the simplest encryption algorithm out there. A Caesar encription "shifts" each individual character forward by a certain number or "key". Each letter in the alphabet is shifted to the letter in the alphabet that is "key" places past the original letter. With a shift value of +1, the string ILIKEZOOS would be rendered as JMJLFAPPT.

Write a method called caesarify that takes two parameters. The first argument is a string you want to encrypt, and the second is an integer that contains the shift value or "key". The function should return a string, which is the input string encrypted with the Caesar cypher using the shift value passed in its second argument. You may assume that the input string is normalized.

Note that the alphabet wraps around, so with a shift value of +1 the Z in ZOOS became an A.

You can also have negative shift values, which cause the alphabet to previous letters. With a -1 shift, the string ILIKEAPPLES would turn into HKHJDZOOKDR.

We will provide you with a function called shiftAlphabet. This function takes one argument, an integer to specify the shift value, and returns a string, which is the uppercase alphabet shifted by the shift value. So if you call shiftAlphabet(2), you will get back the following string: CDEFGHIJKLMNOPQRSTUVWXYZAB

Here is the implementation for shiftAlphabet, which you can just paste into your java file:

public static String shiftAlphabet(int shift) { int start = 0; if (shift < 0) { start = (int) 'Z' + shift + 1; } else { start = 'A' + shift; } String result = ""; char currChar = (char) start; for(; currChar <= 'Z'; ++currChar) { result = result + currChar; } if(result.length() < 26) { for(currChar = 'A'; result.length() < 26; ++currChar) { result = result + currChar; } } return result; } 

Part 5 - Codegroups

Traditionally, encrypted messages are broken into equal-length chunks, separated by spaces and called code groups.

Write a method called groupify which takes two parameters. The first parameter is the string that you want to break into groups. The second argument is the number of letters per group. The function will return a string, which consists of the input string broken into groups with the number of letters specified by the second argument. If there arent enough letters in the input string to fill out all the groups, you should pad the final group with xs. So groupify(HITHERE, 2) would return HI TH ER Ex.

You may assume that the input string is normalized.

Note that we use lower-case x here because it is not a member of the (upper-case) alphabet were working with. If we used upper-case X here we would not be able to distinguish between an X that was part of the code and a padding X.

Part 6 - Putting it all together

Write a function called encryptString which takes three parameters: a string to be encrypted, an integer shift value, and a code group size. Your method should return a string which is its cyphertext equivalent. Your function should do the following:

Call normalizeText on the input string.

Call obify to obfuscate the normalized text.

Call caesarify to encrypt the obfuscated text.

Call groupify to break the cyphertext into groups of size letters.

Return the result

Part 7 - Hacker Problem - Decrypt

Write a method called ungroupify which takes one parameter, a string containing space-separated groups, and returns the string without any spaces. So if you call ungroupify(THI SIS ARE ALL YGR EAT SEN TEN CEx) you will return THISISAREALLYGREATSENTENCE

Now write a function called decryptString which takes three parameters: a string to be decrypted and the integer shift value used to encrypt the string, and returns a string which contains the (normalized) plaintext. You can assume the string was encrypted by a call to encryptString().

So if you were to call

String cyphertext = encryptString(Who will win the election?, 5, 3); String plaintext = decryptString(cyphertext, 5); 

then youll get back the normalized input string WHOWILLWINTHEELECTION.

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Programming Assignment Rubric

The graders should be able to compile and run your program!

If the graders cannot compile and run your program, you will receive a maximum of 20 points on functionality, and a maximum of 20 points on style. These points are given at the graders discretion.

Functionality - 50 points

The graders will test your program in a variety of ways. If your program passes all of their tests, you will receive full credit for functionality. The number of points docked per test will vary from assignment to assignment.

It is up to you to test your code! I expect you to try your program on different inputs before you submit it, to verify that it works correctly.

Your program will be tested on some inputs that are invalid. For example, if you are expected to ask the user for an integer, it is possible that I will enter a string instead of an integer when I run your program. Unless otherwise specified, you can handle this however you want, as long as your program doesnt crash. In general, your program should never crash.

Style - 50 points

You will be graded on a few different style categories:

Comments (10 points)

Each file should have a comment at the top explaining the purpose of the file.

Each method/function should have a comment at the top explaining its purpose.

Inline comments should be used as appropriate - e.g. to explain a particularly dense patch of code.

Indentation, General Use of Whitespace (10 points)

In general, make your code readable.

Blocks within curly braces should be indented by one level. Generally, your

code should line up.

Spaces should be used as appropriate to separate variables from operators,

parameters from each other, etc.

Variable and Function Naming (10 points)

This one is pretty self-explanatory. Give variables and functions names that

describe what they are. Dont make the names too long.

General Cleanliness of Implementation (10 points)

Dont repeat yourself! In other words, dont write the same code twice. Find a

way to unify common code.

Dont allocate memory when you dont have to.

Dont do something wildly inefficient (unless you are specifically instructed to).

Write-up (10 points)

Describe your implementation. Some assignments may have specific questions

that you are expected to answer. If there are no specific questions for an

assignment, just provide a general description of how your program solves the

problem given in the assignment.

Explain how you compiled and ran your program.

Total - 100 points