Design A Class Named Cryptgramjava With The Following Requir

Design A Class Named Cryptgramjava With The Following Requirements

Design a class named Cryptgramjava with the following requirements: create a class named Cryptgram.java that has data members and methods to analyze and encode/decode text based on letter frequencies. The class must contain an array of Letter objects named orderedFrequency, which stores the frequency of each alphabetic letter, sorted by frequency (descending), and alphabetically in case of ties. The methods include: createLetterFrequencyFromFile(File file), which reads a file to generate the letter frequency array; getFrequencyByChar(char letter), which returns the number of times a character appears in the file; encode(String textToBeEncoded), which encrypts the text by replacing each character with the corresponding character from orderedFrequency aligned by rank; and decode(String textToBeDecoded), which reverses the encoding process.

The createLetterFrequencyFromFile method must read a text file, compute the frequency of each letter (A-Z), and store the results in orderedFrequency, sorted primarily by frequency in descending order and secondarily by alphabet order for ties. For example, if 'd' occurs twice, 'r' five times, and 'a' six times, it will be stored accordingly in the array. The getFrequencyByChar method should return the count for a given character, ignoring case. The encode method should replace each character in the input string with the letter at the corresponding position in orderedFrequency, where the most frequent letter in the file corresponds to the first position, and so on, with case ignored. Conversely, the decode method should substitute each character with the original letter based on the encoding scheme, reversing the process.

Paper For Above instruction

The task involves creating a class named Cryptgram.java that analyzes letter frequencies in a text file, then uses this analysis to perform encryption and decryption based on the statistical distribution of letters. This implementation demonstrates core principles in data analysis, string manipulation, and cipher techniques grounded in frequency analysis—an approach historically employed in cryptography to decipher substitution ciphers.

Class Design and Data Members

The principal data member in this class is an array of Letter objects termed orderedFrequency. Each Letter object encapsulates a character and its associated frequency count within the loaded text file. The array must be sorted such that the most frequently occurring letter appears first; in the event of equal frequencies, the array maintains an alphabetical order. This sorted structure underpins the encoding and decoding processes, enabling a substitution cipher founded on real-world letter distributions specific to a given text corpus.

The Letter class should be designed simply with attributes like char letter and int frequency, along with appropriate constructors and getters. These facilitate easy sorting and retrieval operations necessary for implementing the main class.

Method Implementation

createLetterFrequencyFromFile(File file)

This method reads a file and calculates the frequency of each alphabetic letter, ignoring case distinctions. It initializes a temporary frequency array or map for all 26 letters, increments counts as it reads the file line by line, and finally populates the Letter objects with counts. The array is then sorted first by descending frequency, then alphabetically in case of ties. This operation ensures the orderedFrequency array accurately reflects the latest analysis of the input file.

getFrequencyByChar(char letter)

This method accepts a character argument, converts it to lowercase, and searches for its frequency in the computed frequencies. If the letter has appeared in the file, its count is returned; otherwise, zero indicates absence.

encode(String textToBeEncoded)

Encoding proceeds by substituting each letter in the input string with the corresponding letter in the orderedFrequency array based on frequency rank. The most frequent letter in the file maps to the first element, the second most frequent to the second, and so on. Case is ignored during substitution; however, the output maintains the case of the original input where feasible, or can default to uppercase/lowercase as desired.

decode(String textToBeDecoded)

Decoding reconstructs the original message by reversing the substitution. For each character in the encoded string, the method finds its position in the orderedFrequency array and substitutes it with the original letter it represents. This process restores the original text, assuming the same frequency order and mapping were used during encoding.

Testing and Usage

A demo class, such as FrequencyEncryptDriver, is provided to facilitate testing. This driver prompts for the filename and the text to encode, then demonstrates the process of reading the file, analyzing frequencies, encoding, and decoding. Inputs are provided via command-line arguments, for example: java FrequencyEncryptDriver cryptgram.txt "sample text".

Conclusion

The implementation of Cryptgram.java highlights the synergy between statistical analysis and cryptography. By leveraging letter frequency distributions tailored to specific texts, the class enables a form of substitution cipher that adapts dynamically to different text corpora. Such techniques are foundational in cryptography, linguistics, and data analysis, illustrating the application of programming to real-world challenges in secure communication and language processing.

References

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