AP® Computer Science A study guide: a printable PDF built from the College Board's official course and exam description, heaviest topics first.
Last updated 2026 · exam details checked against the College Board's published exam information in 2026
Real pages from the 41-page PDF.
One chapter for each area of the official course and exam description, heaviest topics first.
Multiple-choice questions taken from the guide's chapter quizzes: 4 areas, heaviest first. About 20 minutes, with every answer explained and a score by area. The exam's free-response questions aren't in this quiz: see how the exam works.
Answer: A. The responses may underrepresent residents without paid memberships, so they cannot alone establish access for all residents.. The collection channel favors people already connected to the paid membership service. More responses through that channel do not necessarily cover the residents it misses.
The trap: Removing names addresses one privacy concern, but it does not make the membership-based sample representative.
The collection channel favors people already connected to the paid membership service. More responses through that channel do not necessarily cover the residents it misses.
The trap: Removing names addresses one privacy concern, but it does not make the membership-based sample representative.
int steps = 3;
if (steps < 5)
{
steps += 4;
}
if (steps > 6) { steps -= 2; }
else { steps *= 2; }
System.out.println(steps);Answer: D. 5. The first test changes steps from 3 to 7. The later test is then true and subtracts 2; its else is skipped.
The trap: 7 stops after the earlier if, treating the later decision as an else-if that was never reached.
The first test changes steps from 3 to 7. The later test is then true and subtracts 2; its else is skipped.
The trap: 7 stops after the earlier if, treating the later decision as an else-if that was never reached.
int riders = 19; int seats = 6; double trips = riders / seats; trips += 0.5; System.out.println(trips);
Answer: C. 3.5. The division uses two ints, so it produces 3. Assignment widens that value to 3.0; adding 0.5 gives 3.5.
The trap: 3.6666666666666665 treats the initial division as double division because trips is double.
The division uses two ints, so it produces 3. Assignment widens that value to 3.0; adding 0.5 gives 3.5.
The trap: 3.6666666666666665 treats the initial division as double division because trips is double.
Answer: B. Have each existing method call one helper that accepts the distance and calculates the surcharge.. A distance parameter lets one helper calculate each result while existing public methods keep their contracts.
The trap: Caching the first distance can use the wrong value on later calls.
A distance parameter lets one helper calculate each result while existing public methods keep their contracts.
The trap: Caching the first distance can use the wrong value on later calls.
int[] a={2,5,8,11};
int[] view=a;
for(int i=view.length-1;i>0;i--) {
view[i]=view[i-1];
}
view[0]=0;Answer: D. [0,2,5,8]. view and a reference the same array. Descending indices preserve the old values while shifting them right; the first slot is then replaced with zero.
The trap: [0,2,2,2] is the propagation pattern from copying rightward with increasing indices, which overwrites values before they are used.
view and a reference the same array. Descending indices preserve the old values while shifting them right; the first slot is then replaced with zero.
The trap: [0,2,2,2] is the propagation pattern from copying rightward with increasing indices, which overwrites values before they are used.
Answer: A. (tag != null) && (tag.length() > 0) && tag.substring(0, 1).equals("#"). Conditional AND evaluates left to right. A null reference stops at the guard; an empty String stops at the length test; other Strings reach the content test.
The trap: tag != null || tag.length() > 0 && tag.substring(0, 1).equals("#") accepts any nonnull String and can dereference null.
Conditional AND evaluates left to right. A null reference stops at the guard; an empty String stops at the length test; other Strings reach the content test.
The trap: tag != null || tag.length() > 0 && tag.substring(0, 1).equals("#") accepts any nonnull String and can dereference null.
token.substring(start, start + 3). Which requirement guarantees a valid call for every allowed start?Answer: C. token is nonnull, and 0 ≤ start ≤ token.length() − 3.. The start must be nonnegative and the exclusive end start + 3 cannot exceed the String length. These bounds also require at least three characters.
The trap: 0 ≤ start < token.length() still allows a start near the end, where the requested three-character span exceeds the String.
The start must be nonnegative and the exclusive end start + 3 cannot exceed the String length. These bounds also require at least three characters.
The trap: 0 ≤ start < token.length() still allows a start near the end, where the requested three-character span exceeds the String.
class Tag {
private int value;
public Tag(int value) { value = value; }
public int read() { return value; }
}
Tag t = new Tag(14);
System.out.println(t.read());Answer: B. 0. Both bare names select the parameter; the unassigned instance field keeps its default 0.
The trap: 14 assumes the left side means this.value; the parameter shadows that field.
Both bare names select the parameter; the unassigned instance field keeps its default 0.
The trap: 14 assumes the left side means this.value; the parameter shadows that field.
public static int pairs(int[] a) {
int count=0;
for(int i=0; /* condition */; i++) {
if(a[i]==a[i+1]) count++;
}
return count;
}Answer: C. i < a.length - 1. The second access is i+1, so the last usable i is length-2. The strict bound length-1 includes exactly those starts and runs zero times for arrays shorter than two.
The trap: i < a.length allows i to reach the last index, making a[i+1] an invalid access.
The second access is i+1, so the last usable i is length-2. The strict bound length-1 includes exactly those starts and runs zero times for arrays shorter than two.
The trap: i < a.length allows i to reach the last index, making a[i+1] an invalid access.
Answer: D. (temperature >= 4) && (temperature <= 9). Accepted values must meet both inclusive bounds. This is the negation of temperature < 4 OR temperature > 9.
The trap: temperature >= 4 || temperature <= 9 is true for every integer because at least one of those comparisons always holds.
Accepted values must meet both inclusive bounds. This is the negation of temperature < 4 OR temperature > 9.
The trap: temperature >= 4 || temperature <= 9 is true for every integer because at least one of those comparisons always holds.
The AP® Computer Science A exam is from the College Board. It has 42 multiple-choice questions, plus 4 free-response questions. You get 90 minutes for multiple choice; 3 hours in all, no calculator. The score scale is 1–5 (AP® score scale; your college decides credit). The guide has 4 chapters, one for each area of the official course and exam description; the heaviest is Data Collections at 30–40%.
Source: official AP® Computer Science A page and the official course and exam description. Last updated 2026.
4 chapters, heaviest first, with each area's official weight. The guide's chapters follow this order.
Where to start: the 2 heaviest areas (marked in the map) carry about 27 of the 42 questions. The guide puts them first, so working front to back covers the most points earliest.
The heaviest area is open to read now. The full guide has a chapter for every area, each with all its terms, a quiz and an answer key.
Choose a collection whose structure fits the task, then track both its values and its valid indices. File reading, changing list sizes, two-dimensional traversal, and recursive traces each add their own conditions to check.
Key terms, with examples
String[] names = new String[2]; creates two slots for String references.int[] prices={8,12}; for(int slot=0;slot<prices.length;slot++) prices[slot]/=2; halves both stored prices.int[] a={5,2,9}; int min=a[0]; for(int n:a) if(n<min) min=n; finds 2.File path=new File("readings.txt"); represents a pathname, even before any Scanner opens it.Integer count=5; Double rate=1.25; stores references to immutable numeric wrapper objects.ArrayList<String> notes=new ArrayList<String>(); creates an empty list of String references.for(int i=0;i<a.size();i++) System.out.print(a.get(i)); displays upin.int[][] grid=new int[2][3]; creates two row arrays, each with three integer slots.int[][] g={{1,2},{3,4}};, row-major visitation is 1, 2, 3, 4.int sum=0; for(int r=0;r<g.length;r++) sum+=g[r][1]; totals that column.What this area covers
How the exam asks it
Trace stored values and indices, choose or repair a traversal, and explain when an algorithm meets its specification. Written practice must include complete ArrayList and 2D-array methods. For supplied recursive code, follow calls and returns; for search and sort traces, record the remaining interval or sorted region after each step.
Common traps
Trap 1. Separate three size operations: arrays use a length field, Strings use length(), and ArrayLists use size(). A valid element index is smaller than the relevant count.
Trap 2. A file loop needs suitable data as well as a presence check. hasNext reports another token, but does not promise that nextInt can read it.
Trap 3. Keep coordinate meaning consistent: the first 2D index selects a row. A row count cannot serve as a column bound unless the stated dimensions justify it.
Memory trick
Draw the moving boundary: mark processed entries, the current index, and the remaining region before updating a traversal.
Trace recursion with stacked rows: record each call’s arguments and leave room for its returned value.
The exam has 42 multiple-choice questions, plus 4 free-response questions. The guide sorts the questions into 5 types; spot the type and you'll know what the question wants before you read the choices.
Multiple choice asks for output or a final value after Java statements execute.
Choose a valid constructor or method call using supplied signatures and contracts. Some distractors compile but perform a different call.
Supply a condition, update or code segment that fulfills a specification for every permitted input. This reasoning also supports written free-response solutions.
Free response requires complete methods, constructors or classes from stated requirements. This short choice exercise illustrates one decision; it does not replace a full written response.
Describe an algorithm’s purpose, its required starting conditions or the reason a supplied segment fails.
Pacing: 42 questions in 90 minutes, about 129 seconds a question.
Try the first 8 cards free. Read the term, say the definition out loud, then select the card to check yourself. Arrow keys move between cards.
Follow the steps, then enter your test date. The planner gives you a dated plan that starts with the heaviest areas and saves the last days for review.
Everything on this page is free with no account. The full guide is a PDF you keep.
| Study tool | This page | Full study guide ($5) |
|---|---|---|
| Chapters | A preview of 1 of 4 | All 4 |
| Terms explained | A sample from the open chapters | All 230, each with an example |
| Practice questions | 10 free questions | 40, with an answer key |
| Flashcards | 8 cards | All 230 terms on the self-check list |
| Study plan | Dated planner | 2-, 4- and 8-week plans |
| Cram sheet | — | 2 pages, for the night before |
| Format | Web page | 41-page PDF, printable |
We built one chapter for each area of the College Board's official course and exam description for AP® Computer Science A, using its published weights to order the chapters and size the quizzes. Each chapter was written, then fact-checked against the official exam information in a separate review. The exam details were checked against the College Board's published exam information in 2026.
Sources: official AP® Computer Science A page, official course and exam description. Last updated 2026.
AP® is a trademark registered by the College Board, which is not affiliated with, and does not endorse, this guide. TransferCredit.org is independent and not affiliated with the College Board. © 2026 UPI Globale Edu Inc.
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