AP Computer Science A FRQ Practice Guide

title: "AP Computer Science A FRQ Practice Guide" description: "Master the four FRQ archetypes: methods, class design, array/ArrayList, and 2D arrays. Common Java pitfalls, worked examples, and scoring strategies." date: "2026-01-15" examDate: "May AP Exam" topics:

• FRQ Patterns
• Common Pitfalls
• Worked Examples
• Scoring Rubrics

FRQs make up 50% of your AP CS A score (36 out of 108 points). The four FRQs follow predictable patterns. Learn them, and you'll know exactly what to do on exam day.

You have 90 minutes total for 4 FRQs — roughly 22 minutes per problem. Don't spend 40 min perfecting one; get partial credit on all four instead.

The Four FRQ Archetypes

FRQ 1: Methods and Control Structures (~9 pts, 20 min)

What it asks: Write a single method (no class design) that uses loops and conditionals.

Typical scenario:

• Parse a String or array.
• Return a count, sum, index, or boolean.
• Use .substring(), .indexOf(), modulo, or array access.

Example prompt: "Write a method countVowels(String s) that returns the number of vowels in the string. Vowels are a, e, i, o, u (both cases)."

Rubric focus:

• Method signature correct (parameter type, return type).
• Logic correct (handles all cases).
• Syntax correct (no compilation errors).

High-yield mistakes to avoid:

• Forgetting return statement.
• Using == to compare Strings.
• Off-by-one in loop bounds.
• Integer division when you meant floating-point.

FRQ 2: Class Design (~9 pts, 20 min)

What it asks: Write a complete class with constructor, instance variables, and 2-3 methods.

Typical scenario:

• You're given a description (e.g., "A student has a name, GPA, and major").
• Write the constructor to initialize all fields.
• Write getter/setter methods or action methods (e.g., addCourse(), updateGPA()).
• Often includes inheritance (subclass of a given superclass).

Example prompt: "Write a class Student with fields name, gpa, and courses (an ArrayList). Include a constructor and a method addCourse(String courseName) that adds to the list. Also write a method isHonors() that returns true if GPA >= 3.5."

Rubric focus:

• Constructor initializes all fields.
• Instance variables declared correctly (right types).
• Methods have correct signature and logic.
• No stray syntax errors.

High-yield mistakes to avoid:

• Forgetting this keyword in constructor when assigning parameters to fields.
• Wrong return type (e.g., returning void when you should return a value).
• ArrayList without generics: ArrayList instead of ArrayList<String>.

FRQ 3: Array/ArrayList Manipulation (~9 pts, 20 min)

What it asks: Write one or two methods that traverse and manipulate an array or ArrayList.

Typical scenario:

• Remove all elements matching a condition.
• Shift or rearrange elements.
• Count, sum, or find based on a criterion.

Example prompt: "Write a method removeNegatives(ArrayList<Integer> numbers) that removes all negative numbers from the list. This method has no return value (void)."

Rubric focus:

• Correct traversal (index vs enhanced for-loop chosen wisely).
• Correct remove/modify logic.
• No skipped elements (if removing, iterate backwards or use a new list).

High-yield mistakes to avoid:

• Removing during forward iteration (skips next element).
• Using .get(i) on an ArrayList after .remove() without updating the index.
• Forgetting .size() is dynamic (recalculate each loop iteration if you use it).

FRQ 4: 2D Array Traversal (~9 pts, 20 min)

What it asks: Write one or two methods that traverse a 2D array using nested loops.

Typical scenario:

• Sum/find max in all elements, or per row/column.
• Find a specific position or pattern.
• Check if all rows satisfy a condition.

Example prompt: "Write a method rowSum(int[][] matrix, int row) that returns the sum of all elements in the specified row. Also write a method findValue(int[][] matrix, int target) that returns the position [row][col] of target, or null if not found."

Rubric focus:

• Nested loop structure (outer = row, inner = column).
• Correct array access [row][col].
• Correct logic (sum, search, or whatever is asked).

High-yield mistakes to avoid:

• Swapped row/col indices (accessing [col][row] instead of [row][col]).
• Incorrect loop bounds (forgetting matrix.length vs matrix[0].length).
• Off-by-one in nested loop iteration.

Common Java Pitfalls (Scoring Table)

| Pitfall | Example | Fix | Points Lost | |---|---|---|---| | Using == on Strings | if (s == "hello") | Use .equals(s, "hello") or s.equals("hello") | 1-2 pts | | Integer division instead of cast | double avg = total / count; | double avg = (double) total / count; | 1-2 pts | | Forgetting return statement | Method ends with } but no return | Add return value; before final } | 2-3 pts | | Off-by-one in loop | for (int i = 0; i <= arr.length; i++) | Use i < arr.length (or i < size for ArrayList) | 1-2 pts | | ArrayList remove during iteration | Loop forward, remove, skip next | Loop backwards or use separate list | 2-3 pts | | Wrong array access | arr[col][row] in 2D array | Should be arr[row][col] | 1-2 pts | | Null pointer exception | Call method on uninitialized object | Check for null or initialize before use | 1-3 pts | | ArrayList without generics | ArrayList list = new ArrayList(); | Use ArrayList<Integer> or ArrayList<String> | 0-1 pts (warning only) | | Missing .substring() bounds | s.substring(0, s.length() + 1) | Bounds are [0, s.length()) (end exclusive) | 1 pt | | Constructor doesn't initialize fields | Constructor empty; fields are null | Call this.field = param; in constructor | 2-3 pts |

Worked Example 1: Class Design (FRQ 2 Pattern)

Prompt: "Write a class Course that stores a course name and enrollment list (ArrayList of student names). Include a constructor that takes a course name, a method enrollStudent(String name) that adds a student, and a method getEnrollment() that returns the number of students."

Solution:

public class Course {
    private String courseName;
    private ArrayList<String> students;
    
    public Course(String name) {
        this.courseName = name;
        this.students = new ArrayList<String>();
    }
    
    public void enrollStudent(String name) {
        students.add(name);
    }
    
    public int getEnrollment() {
        return students.size();
    }
}

Scoring checklist:

• ✅ Fields declared with correct types and access modifier (private).
• ✅ Constructor initializes both fields.
• ✅ enrollStudent() uses .add() correctly.
• ✅ getEnrollment() returns an int (.size()).
• ✅ No syntax errors, no null pointer risks.

Worked Example 2: Array Algorithm (FRQ 3 Pattern)

Prompt: "Write a method removeDuplicates(ArrayList<Integer> numbers) that removes all duplicate values, keeping only the first occurrence. The method has no return value."

Solution:

public void removeDuplicates(ArrayList<Integer> numbers) {
    int i = 0;
    while (i &lt; numbers.size()) {
        Integer current = numbers.get(i);
        int j = i + 1;
        while (j &lt; numbers.size()) {
            if (numbers.get(j).equals(current)) {
                numbers.remove(j);
            } else {
                j++;
            }
        }
        i++;
    }
}

Scoring checklist:

• ✅ Nested loop structure (outer advances, inner removes).
• ✅ Removal handled correctly (inner loop does not increment j on remove).
• ✅ Uses .equals() to compare Integers (not ==).
• ✅ .size() recalculated each iteration (necessary for shrinking list).
• ✅ No syntax errors.

💡 Alternative: Build a new ArrayList with only first occurrences, then call numbers.clear() and addAll() — simpler and avoids the loop pitfall.

FRQ Day-Of Strategy

1. Scan all 4 FRQs in the first 3 minutes. Identify which looks easiest.
2. Start with your easiest FRQ. Psychological boost; you're working for 5+ minutes before risking a blank answer.
3. Allocate ~22 min per FRQ. After 22 min, move on even if incomplete.
4. Write pseudocode first for hard FRQs. 1 min of pseudocode saves 5 min of coding errors.
5. Do not obsess over one line. Get partial credit on all four rather than perfect on two.

Scoring Rules You Should Know

• Partial credit is real: A method with correct logic but a missing semicolon can score 7-8 out of 9 points.
• Syntax errors are forgiving: As long as the intent is clear, minor typos don't tank you.
• Off-by-one in one place: If your loop is i <= arr.length (one too many), you'll lose 1-2 points, not 9.
• Wrong return type: Returning void when you should return int is a big error (-3 pts), but everything else might be fine.

Related guides:

• 3-day cram plan
• 7-day study plan
• Last-minute review