There is a large wealth of resources available to assist in preparation for the AP Computer Science A exam.
In no particular order, some of them are listed here:
Course and Exam Description: This is the core document for the AP CSA course, and this review guide is largely based off of this since it provides a listing of all the essential knowledge assessed on the AP Exam.
AP CSA Java Quick Reference: This Quick Reference sheet will be provided to exam-takers for both the MCQ and FRQ sections of the AP Exam.
Released Free-Response Questions, 2021
Released Free-Response Questions, 1999-2020: These are all of the publicly-available Free-Response Questions from past AP Exams.
AP Computer Science A Exam Tips: This provides a few general pointers for the exam.
Writing Code on the AP Computer Science Exams: Important Advice for Students: A partially outdated, yet still very relevant, resource with some comments on writing FRQ responses.