Implement iterators and write tests in Java

In Java, write everything from scratch (no IDE scaffolding): 1) Define a generic Iterator<T> interface with hasNext() and next(). 2) Implement ArrayIterator<T> over a fixed array. 3) Implement PeekingIterator<T> that wraps any Iterator<T> and adds peek() without advancing. 4) Provide minimal unit tests that compile and run, covering empty input, single element, multiple elements, and calling next() when no elements remain. Analyze time/space complexity and edge cases.