Java Programming Cheatsheet - Princeton University
Data Structure Visualizations - David Galles [University of San Francisco]
Sorting Visualizations - Algorithms, hackerearth.com
Comparison Sorting Algorithms - University of San Francisco
Programs
Beaver Works Summer Institute - https://beaverworks.ll.mit.edu/CMS/bw/bwsi
Free Java Online Courses
CSAwesome - https://runestone.academy/ns/books/published/csawesome/index.html
Java Review for the AP CS A Exam - Georgia Institute of Technology - http://ice-web.cc.gatech.edu/ce21/1/static/JavaReview-RU/index.html
AP Computer Science in Java (MOCHA) - https://codehs.com/course/53
CS50 Course at Harvard - https://cs50.harvard.edu/
Complete Java Masterclass - Udemy - https://www.udemy.com/java-the-complete-java-developer-course/
Decoding AP Computer Science A - Udemy - https://www.udemy.com/decoding-ap-computer-science-a/
Introduction to Computer Science using Java - http://chortle.ccsu.edu/CS151/cs151java.html
Java Tutorial for Complete Beginners - https://www.udemy.com/java-tutorial/#/
AP Computer Science - Georgia Virtual Learning - http://www.gavirtuallearning.org/Resources/CTAEResources/CTAEShared/SharedAPComputerScience.aspx
Java Review for the AP CS A Exam - http://interactivepython.org/runestone/static/JavaReview/index.html
Self Test Multiple Choice Questions - Introduction to Java Programming, Ninth Edition - http://www.cs.armstrong.edu/liang/intro9e/test.html
Teach yourself Java in 21 days - http://www.cs.cmu.edu/afs/cs.cmu.edu/user/gchen/www/download/java/LearnJava.pdf
Java - Emory University - http://math.oxford.emory.edu/site/cs170/
Introduction to Programming in Java - http://introcs.cs.princeton.edu/java/home/
Code Academy - https://www.codecademy.com/
Advanced Placement - AP Computer Science A Review Sessions - https://www.youtube.com/watch?v=fQ6bxFQFldQ&list=PLoGgviqq4845xKOY11PnkE7aqJC7-bYrd
Java Programming All-in-One Tutorial Series (6 HOURS!) - https://www.youtube.com/watch?v=r3GGV2TG_vw
AP Computer Science A Units YouTube - https://www.youtube.com/playlist?list=PLmpmyPywZ440vPqpAPeUkE-TeKifbS45W
Practices
CodingBat - http://codingbat.com
CodeStepByStep - https://codestepbystep.com
LeetCode - https://leetcode.com
Practice-It - http://practiceit.cs.washington.edu/
Rosetta Code - http://rosettacode.org
CodeHS - https://codehs.com/
GeeksforGeeks - http://www.geeksforgeeks.org/
Codewars - https://www.codewars.com/
Project Euler - https://projecteuler.net/
Competitions
picoCTF - CMU Cybersecurity Competition - https://picoctf.com/
USA Computing Olympiad - http://www.usaco.org/
Tools/Software
Java Visualizer - https://cscircles.cemc.uwaterloo.ca/java_visualize/
visualgo.net - https://visualgo.net/en/
SQLZOO - https://sqlzoo.net/wiki/SQL_Tutorial
Tinkercad - https://www.tinkercad.com/
Figma - https://www.figma.com/
Reading
The Book: Blown to Bits (Abelson, Ledeen, Lewis) - http://www.bitsbook.com/