The Stacks
AP COMPUTER SCIENCE

AP Computer Science A

Java, from first program to recursion, organized exactly as the College Board's revised 2025–26 Course and Exam Description lays it out: four units, 53 numbered topics. This is the new framework — inheritance is gone, text files and data sets are in, and everything is typed into Bluebook. Each topic page has the essential knowledge, a worked code example, an exam tip, practice questions in the exam's style, and vocabulary.

The 4 units

Weight shown is that unit's share of the multiple-choice exam.

How the exam works

  • Section I — Multiple choice. 42 questions, 90 minutes, 50% of your score. Heavy on code reading: predict output, count iterations, find the bug, pick the equivalent code.
  • Section II — Free response. 4 questions, 90 minutes, 50% of your score. The four types are fixed every year: Q1 Methods and Control Structures, Q2 Class Design (write an entire class), Q3 Data Analysis with ArrayList, Q4 2D Array. Each is scored on a 9-point rubric.
  • The exam is fully digital in the Bluebook app — you type Java directly. No paper, no handwritten code.
  • A Java Quick Reference is provided with the exact String, Math, ArrayList, Integer, Double, and Object methods you can use. If a method isn't on it, don't assume it exists on the exam.
  • No penalty for guessing on multiple choice. On FRQs, partial credit is real — a correct loop with a wrong condition still earns points, and a blank earns nothing.

What separates a 5 from a 3

  • Trace with a table, every time. Variables, loop counters, array contents after each pass. Most multiple-choice misses are tracing slips, not knowledge gaps.
  • Know the three String traps cold: substring's end index is exclusive, == compares references not contents (use .equals), and compareTo returns an int, not a boolean.
  • Write FRQs in a fixed shape. Method header exactly as given → declare a result variable → loop → conditional → update → return. Practice until it's automatic; rubric points reward each piece independently.
  • Off-by-one is the whole game in Unit 4. Arrays start at 0 and end at length - 1. Removing from an ArrayList inside a forward loop skips elements. Row-major vs. column-major traversal of a 2D array changes the output order.
  • Unit 4 is 30–40% of the exam. Arrays, ArrayLists, 2D arrays, and the two algorithms (search, sort) plus recursion tracing. Study time should reflect that.

Practice tracing

Interactive, step-by-step walkthroughs of the loops, lists, and recursion the exam asks you to trace by hand.

▶Code tracerinteractive