Add new Algorithm - Fast Exponentiation Algorithm (in JAVA)

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Add Fast Exponentiation (Exponentiation by Squaring) Algorithm to the Java Algorithm Template

Problem: Currently, the Java algorithm template does not include an efficient implementation of the fast exponentiation algorithm (also known as exponentiation by squaring). This algorithm is important for efficiently calculating large powers in algorithms related to number theory, cryptography, and modular arithmetic.

Proposed Solution:I suggest adding an implementation of the fast exponentiation algorithm to the Java algorithm template. This algorithm should be able to handle both positive and negative exponents efficiently. The time complexity of this algorithm is O(log n), making it much faster than the naive O(n) approach.(under a certain module)