Description
You will be writing a replacement for Java’s BigInteger to perform multiplications and to run the extended
Euclidean algorithm on integer values that would overflow long .
1. You are provided with the start of a class to process arbitrarily-sized integers called HeftyInteger .
HeftyInteger objects are represented internally as two’s-complement raw integers using byte arrays
(i.e., instances of byte[] ).
1. Currently, HeftyInteger has the following operations implemented:
A constructor that creates a new HeftyInteger object based on a provided byte[] .
A method to compute the sum of two HeftyInteger objects.
A method to determine the negation of a HeftyInteger object.
A method to compute the difference of two HeftyInteger objects.
Several other helper methods.
2. Due to the use of a two’s complement representation of the integers, positive HeftyInteger
objects should always have at least one leading 0 bit (indicating that the integer is positive) in their
byte[] representation. This property may cause the array to be bigger than expected (e.g., a
1024-bit positive integer will be represented using a length 129 byte array).
3. HeftyIntegers are represented using a big-endian byte-order, so the most significant byte is at index 0
of the byte[] .
4. You will further need to implement the following functions:
HeftyInteger multiply(HeftyInteger other)
HeftyInteger[] XGCD(HeftyInteger other)
Any additional helper functions that you deem necessary.
5. You may not use any calls the Java API class java.math.BigInteger or any other JCL class
within HeftyInteger .
2. Once HeftyInteger is complete, make sure your implementation of HeftyInteger can be used
to run the driver programs contained in MultiplicationTest.java and XgcdTest.java . To get
full credit, your implementation should be efficient enough to complete multiplication or XGCD given 200-
digit inputs within 3 minutes.
DO NOT upload any IDE package files.
You must be able to compile the driver programs by running javac MultiplicationTest.java
and javac XgcdTest.java , respectively.
You must be able to run the driver program by running java MultiplicationTest and
java XgcdTest , respectively.
You must fill out info_sheet.txt .
The project is due at the precise date and time stated above. Upload your progress to Box frequently,
even far in advance of this deadline. No late assignments will be accepted. At the deadline, your Box
folder will automatically be changed to read-only, and no more changes will be accepted. Whatever is
present in your Box folder at that time will be considered your submission for this assignment—no other
submissions will be considered.
Feature Points
multiply 40
XGCD 55
Assignment info sheet/submission 5
Submission Guidelines
Grading Rubric
HeftyInteger
