AP CSA Practice Exam #2

March 30, 2026

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AP Computer Science A
Full Practice Exam #2

42 Multiple-Choice Questions • 2025-2026 Curriculum • Units 1-4

Error-Spotting • I/II/III Analysis • Output Tracing • 90 Minutes

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Unit 1: Primitive Types, Objects & Methods (Q1-10)

Question 1Error Spotting

A student writes the following to compute the average of two integers. Which statement BEST describes the bug?

int a = 7;
int b = 2;
double avg = a / b;
System.out.println(avg);

A.Variables a and b must be declared double to prevent a compile error. B.Integer division truncates before assignment, so avg stores 3.0 instead of 3.5. C.Java automatically promotes both operands to double when assigned to a double variable, so the output is correct. D.The output will be 3 because println truncates doubles to integers.

Correct Answer: B. Integer division happens before assignment. 7 / 2 evaluates to 3 (int), then widens to 3.0. Fix: (double) a / b or a / (double) b.

Question 2Output Trace

What is printed?

String word = "Computer";
System.out.println(word.substring(0, 4).toUpperCase());

A.COMP B.COMPU C.COMPUTER D.comp

Correct Answer: A. substring(0,4) extracts indices 0-3: "Comp". toUpperCase() gives "COMP". The end index is exclusive.

Question 3Output Trace

What value is stored in result?

int x = 17;
int result = (x / 5) * 5 + (x % 5);

A.15 B.17 C.20 D.2

Correct Answer: B. x/5 = 3; 3*5 = 15; x%5 = 2; 15+2 = 17. This expression always reconstructs the original integer value.

Question 4I / II / III

Given: double p = -4.2; double q = 1.8; Which of the following evaluate to a value greater than 4?

Math.abs(p)
Math.pow(q, 3)
Math.sqrt(25.0)

A.I only B.I and III only C.II and III only D.I, II, and III

Correct Answer: D. I: |-4.2| = 4.2 > 4. II: 1.8^3 = 5.832 > 4. III: sqrt(25) = 5.0 > 4. All three exceed 4.

Question 5Error Spotting

The code below causes a runtime error. What is the cause?

String name = null;
int len = name.length();
System.out.println(len);

A.Compile error: null cannot be assigned to a String reference. B.Runtime NullPointerException: a method is called on a null reference. C.length() returns 0 for null strings, so len stores 0. D.Runtime ArrayIndexOutOfBoundsException: the string has no characters.

Correct Answer: B. Assigning null to a reference variable compiles fine. Calling any instance method on null throws a NullPointerException at runtime.

Question 6Output Trace

What is printed?

int m = 3;
int n = 4;
System.out.println("Sum: " + m + n);
System.out.println("Sum: " + (m + n));

A.Sum: 34 then Sum: 7 B.Sum: 7 then Sum: 7 C.Sum: 34 then Sum: 34 D.Compile error on line 3

Correct Answer: A. Left-to-right: "Sum: " + 3 = "Sum: 3", then + 4 = "Sum: 34". Parentheses in line 2 force arithmetic first: (3+4)=7, giving "Sum: 7".

Question 7Output Trace

What value is stored in z?

double d = 9.99;
int z = (int)(d * 10) % 7;

A.1 B.2 C.6 D.0

Correct Answer: A. d*10 = 99.9. Cast truncates to 99. 99 % 7 = 1 (since 14x7=98, 99-98=1).

Question 8I / II / III

After this executes, which statements are TRUE?

int alpha = 10;
int beta = 3;
alpha -= beta;
beta *= alpha;
alpha += beta;

alpha equals 28
beta equals 21
alpha + beta equals 49

A.I only B.I and II only C.II and III only D.I, II, and III

Correct Answer: D. alpha-=3 gives 7. beta*=7 gives 21. alpha+=21 gives 28. All three statements are true: alpha=28, beta=21, sum=49.

Question 9Concept

A program must generate a random integer from 5 to 12 inclusive. Which expression is correct?

A.(int)(Math.random() * 8) + 5 B.(int)(Math.random() * 7) + 5 C.(int)(Math.random() * 12) + 5 D.(int)(Math.random() * 8) + 4

Correct Answer: A. Range = 12-5+1 = 8. Formula: (int)(Math.random() * range) + min. B gives [5,11]; C gives [5,16]; D gives [4,11].

Question 10Error Spotting

This method is supposed to return twice the absolute value of its parameter. What is wrong?

public static int doubleAbs(int val) {
    if (val < 0) {
        val = -val;
    }
    val = val * 2;
}

A.Parameters cannot be reassigned inside a method body. B.The method is missing a return statement, causing a compile error. C.The negation -val causes overflow when val = 0. D.The method should be private rather than static.

Correct Answer: B. The return type is int but no return statement exists — compile error. Reassigning parameters is perfectly legal in Java.

Unit 2: Selection and Iteration (Q11-21)

Question 11Error Spotting

A student writes the following to assign a letter grade. What actually prints for score = 85?

int score = 85;
String grade;
if (score >= 90) {
    grade = "A";
}
if (score >= 80) {
    grade = "B";
}
if (score >= 70) {
    grade = "C";
}
else {
    grade = "F";
}
System.out.println(grade);

A.B — the second condition correctly matches. B.C — separate ifs keep running and overwrite the grade. C.F — the final else always executes. D.Compile error — grade may not be initialized on all paths.

Correct Answer: B. Each if runs independently. score=85: first if skips, second sets grade="B", third sets grade="C". The else pairs only with the third if and does not run since 85>=70. Final output: C. Fix: use else if.

Question 12I / II / III

Which are equivalent to !(x > 5 && y <= 10)?

x <= 5 || y > 10
!(x > 5) || !(y <= 10)
x <= 5 && y > 10

A.I only B.I and II only C.II and III only D.I, II, and III

Correct Answer: B. De Morgan's Law: !(A && B) = !A || !B. I and II are both equivalent. III uses && instead of || — not equivalent.

Question 13Output Trace

What is printed?

int ctr = 1, total = 0;
while (ctr <= 5) {
    if (ctr % 2 != 0) {
        total += ctr;
    }
    ctr++;
}
System.out.println(total);

A.6 B.9 C.15 D.25

Correct Answer: B. Adds odd numbers 1-5: 1+3+5 = 9.

Question 14Error Spotting

Which loop header has an off-by-one error when intending to iterate over integers 1 through n inclusive?

A.for (int i = 1; i <= n; i++) B.for (int i = 1; i < n + 1; i++) C.for (int i = 1; i < n; i++) D.for (int i = 0; i < n; i++) printing i+1 each iteration

Correct Answer: C. Option C stops at i = n-1, missing value n. Options A, B, and D all correctly cover 1 through n.

Question 15Output Trace

What is printed?

int count = 0;
for (int r = 0; r < 4; r++) {
    for (int c = r; c < 4; c++) {
        count++;
    }
}
System.out.println(count);

A.16 B.12 C.10 D.6

Correct Answer: C. r=0: 4 iterations. r=1: 3. r=2: 2. r=3: 1. Total = 4+3+2+1 = 10.

Question 16I / II / III

This for loop computes 6! (720). Which while loops produce the same result?

int product = 1;
for (int k = 1; k <= 6; k++) { product *= k; }

int k = 1, product = 1;
while (k <= 6) { product *= k; k++; }

int k = 1, product = 1;
while (k < 7) { k++; product *= k; }

int k = 0, product = 1;
while (k < 6) { k++; product *= k; }

A.I only B.I and II only C.I and III only D.II and III only

Correct Answer: C. I multiplies k=1 through 6 in order — correct. II increments before multiplying so it computes 2x3x4x5x6x7 — wrong. III starts k=0, increments to 1 first, then multiplies: 1x2x3x4x5x6 — correct.

Question 17Output Trace

What does mystery("abcde") return?

public static String mystery(String s) {
    String result = "";
    for (int i = s.length() - 1; i >= 0; i -= 2) {
        result += s.charAt(i);
    }
    return result;
}

A."eca" B."edcba" C."ace" D."db"

Correct Answer: A. i=4 picks 'e'; i=2 picks 'c'; i=0 picks 'a'; i=-2 stops. result = "eca".

Question 18I / II / III

getValue() has a side effect (it prints "called"). With x = 0, this runs:

boolean r = (x != 0) && (getValue() > 0);

r is false
getValue() is NOT called due to short-circuit evaluation
"called" is printed to the console

A.I only B.I and II only C.II and III only D.I, II, and III

Correct Answer: B. x=0 makes x != 0 false. && short-circuits: right side never evaluates. So r=false (I true), getValue() not called (II true), "called" not printed (III false).

Question 19Error Spotting

Which loop runs indefinitely?

A.int n = 10; while (n != 0) { n -= 3; } B.int n = 1; while (n < 100) { n *= 2; } C.int n = 0; while (n < 10) { n++; } D.int n = 100; while (n > 0) { n -= 10; }

Correct Answer: A. n: 10, 7, 4, 1, -2, -5... It skips over 0, so n != 0 is always true. Option D terminates correctly at n=0.

Question 20Output Trace

What is printed?

int p = 6, q = 4;
if (p > 5) {
    if (q > 5) {
        System.out.println("A");
    }
    else {
        System.out.println("B");
    }
} else if (p > 3) {
    System.out.println("C");
} else {
    System.out.println("D");
}

A.A B.B C.C D.D

Correct Answer: B. p=6>5 true, enter outer if. q=4>5 false, take else branch: prints B.

Question 21Output Trace

What is printed?

int n = 16;
int count = 0;
while (n > 1) {
    n = n / 2;
    count++;
}
System.out.println(count);

A.3 B.4 C.5 D.16

Correct Answer: B. 16→8→4→2→1. Loop runs 4 times before n=1 fails the condition. This computes log base 2 of 16.

Unit 3: Class Creation (Q22-32)

Question 22Error Spotting

What is wrong with this constructor?

public class Thermometer {
    private double temperature;

    public Thermometer(double temperature) {
        temperature = temperature;
    }
}

A.The constructor parameter should be int, not double. B.temperature = temperature assigns the parameter to itself; the instance variable stays at 0.0. C.The constructor name must differ from the class name to avoid a conflict. D.The instance variable must be public for the constructor to access it.

Correct Answer: B. The parameter shadows the instance variable. The assignment sets the parameter to itself. Fix: this.temperature = temperature;

Question 23I / II / III

Given: Counter c1 = new Counter(); Counter c2 = c1; c1.increment(); c1.increment(); Which statements are TRUE?

c1.getCount() returns 2
c2.getCount() returns 0
c1 and c2 refer to the same object in memory

A.I only B.I and III only C.II and III only D.I, II, and III

Correct Answer: B. c2 = c1 copies the reference — both point to the same object (III true). After two increments, both return 2. So I is true; II is false (c2.getCount() = 2, not 0).

Question 24Concept

Which is the BEST reason to declare instance variables private?

A.Private variables execute faster at runtime than public ones. B.Private variables can only be accessed through public methods, enforcing encapsulation and enabling validation. C.Private variables are automatically initialized; public variables require explicit initialization. D.Private variables prevent the class from being instantiated more than once.

Correct Answer: B. Encapsulation hides data behind controlled methods. A, C, and D are false statements about access modifiers in Java.

Question 25Error Spotting

What error will this method cause?

public class BankAccount {
    private double balance;

    public boolean isRich(double threshold) {
        if (balance > threshold) {
            return true;
        } else if (balance < threshold) {
            return false;
        }
    }
}

A.Should use == instead of > for floating-point comparison. B.Compile error: not all code paths return a value (when balance == threshold). C.Runtime exception thrown when balance exactly equals threshold. D.balance is private and cannot be read inside the same class.

Correct Answer: B. When balance == threshold neither branch executes — no return statement. Java compiler requires all paths to return a value. Fix: add return false; after the if-else.

Question 26Output Trace

The Dog class overrides toString() to return name + " (" + age + ")". What is printed?

Dog d = new Dog("Rex", 3);
System.out.println(d);

A.The memory address of the Dog object B.Rex (3) C.Dog@hashcode because println cannot call toString automatically D.Compile error: println does not accept object parameters

Correct Answer: B. println(obj) calls toString() automatically. Since it's overridden, output is Rex (3). Without the override, C would occur.

Question 27I / II / III

Rectangle r = new Rectangle(4, 6) with private fields width=4, height=6. Which statements are TRUE?

r.area() returns 24
r.perimeter() returns 20
r.width can be accessed directly from client code

A.I only B.I and II only C.II and III only D.I, II, and III

Correct Answer: B. I: 4x6=24. II: 2x(4+6)=20. III: width is private — direct access from client code causes a compile error.

Question 28Concept

A setGPA(double g) setter should reject values outside [0.0, 4.0]. Which implementation is CORRECT?

A.if (g > 0.0 && g < 4.0) { gpa = g; } B.if (g >= 0.0 && g <= 4.0) { gpa = g; } C.if (g >= 0.0 || g <= 4.0) { gpa = g; } D.if (!(g < 0.0) || !(g > 4.0)) { gpa = g; }

Correct Answer: B. A uses strict inequalities, excluding 0.0 and 4.0. C and D use || which is always true for any finite number. Only B correctly accepts the closed interval [0.0, 4.0].

Question 29Error Spotting

Which statement about this class is TRUE?

public class Coin {
    private String side = "heads";

    public void flip() {
        side = (Math.random() < 0.5) ? "tails" : "heads";
    }

    public static String getSide() {
        return side;
    }
}

A.The class compiles and works correctly. B.getSide() causes a compile error: a static method cannot reference the non-static field side. C.flip() causes a compile error because the ternary operator is not allowed in assignments. D.A runtime exception is thrown when getSide() is called before flip().

Correct Answer: B. A static method cannot access non-static (instance) fields. Fix: remove static from getSide().

Question 30Output Trace

What is printed?

public class Multiplier {
    private int factor;
        public Multiplier(int f) {
        factor = f;
    }
        public int apply(int n) {
        return n * factor;
    }
    public Multiplier combine(Multiplier other) {
        return new Multiplier(factor * other.factor);
    }
}
// Client:
Multiplier triple = new Multiplier(3);
Multiplier dbl    = new Multiplier(2);
Multiplier six    = triple.combine(dbl);
System.out.println(six.apply(5));

A.15 B.25 C.30 D.Compile error: other.factor is a private field

Correct Answer: C. triple.combine(dbl) creates Multiplier(3x2=6). six.apply(5) = 5x6 = 30. Private fields are accessible within the same class, including via a parameter reference.

Question 31I / II / III

Constructor: public Car(String make, int year). Which create a valid Car object?

Car c = new Car("Toyota", 2024);
Car c = new Car(2024, "Toyota");
Car c = new Car("Honda", 1999);

A.I only B.I and II only C.I and III only D.I, II, and III

Correct Answer: C. Constructor requires (String, int). I: ("Toyota",2024) valid. II: (2024,"Toyota") reverses types — compile error. III: ("Honda",1999) valid.

Question 32Error Spotting

A student compares two String objects. What is wrong?

String s1 = new String("hello");
String s2 = new String("hello");
if (s1 == s2) {
    System.out.println("equal");
} else {
    System.out.println("not equal");
}

A.Compiles and correctly prints equal because both contain the same characters. B.== compares object references, not content. Two distinct objects print not equal. C.A runtime NullPointerException is thrown because string literals cannot use new. D.== on strings is only valid when comparing to null.

Correct Answer: B. == compares references. new String("hello") creates two separate heap objects, so == is false. Use .equals() to compare content.

Unit 4: Data Collections — Arrays & ArrayLists (Q33-42)

Question 33Error Spotting

What error occurs when this runs?

int[] nums = {10, 20, 30, 40, 50};
for (int i = 0; i <= nums.length; i++) {
    System.out.println(nums[i]);
}

A.Compile error: array initializer syntax is invalid. B.Runtime ArrayIndexOutOfBoundsException when i = 5; valid indices are 0-4. C.The loop runs only 4 times, missing the last element. D.Runtime NullPointerException at index 5.

Correct Answer: B. i <= nums.length allows i=5. Valid indices are 0-4, so nums[5] throws ArrayIndexOutOfBoundsException. Fix: i < nums.length.

Question 34Output Trace

What is printed?

int[] data = {3, 1, 4, 1, 5, 9, 2, 6};
int maxVal = data[0];
for (int val : data) {
    if (val > maxVal) {
        maxVal = val;
    }
}
System.out.println(maxVal);

A.3 B.6 C.9 D.31

Correct Answer: C. Tracks maximum: 3→4→5→9. Maximum in array is 9.

Question 35Error Spotting

A student tries to double every element. Why does this NOT work?

int[] scores = {70, 80, 90};
for (int s : scores) {
    s = s * 2;
}
System.out.println(scores[0]);

A.The enhanced for loop does not allow arithmetic on the loop variable. B.s is a copy; modifying s does not change the original array. Prints 70. C.The code correctly prints 140. D.A runtime exception is thrown because primitive arrays cannot use enhanced for.

Correct Answer: B. Enhanced for creates a local primitive copy. Modifying it doesn't affect the array. Fix: use an indexed loop

for (int i=0; i

Question 36I / II / III

ArrayList words starts as ["cat","dog","bird"]. After words.add(1,"fish"); then words.remove(2); which are TRUE?

words.size() returns 3
words.get(0) returns "cat"
words.get(1) returns "dog"

A.I only B.I and II only C.II and III only D.I, II, and III

Correct Answer: B. Start: ["cat","dog","bird"]. After add(1,"fish"): ["cat","fish","dog","bird"]. After remove(2): ["cat","fish","bird"]. Size=3 (I true), get(0)="cat" (II true), get(1)="fish" not "dog" (III false).

Question 37Error Spotting

A student removes all even numbers from an ArrayList. What is the bug?

ArrayList nums = new ArrayList<>(Arrays.asList(1,2,3,4,5,6));
for (int i = 0; i < nums.size(); i++) {
    if (nums.get(i) % 2 == 0) {
        nums.remove(i);
    }
}

A.The remove method requires a cast to use index-based removal on an Integer list. B.After removal, indices shift left. The element after each removed element is skipped, so some even numbers are missed. C.The code compiles and correctly removes all even numbers. D.A ConcurrentModificationException is always thrown when removing with an index loop.

Correct Answer: B. Removing element at index i shifts the next element to index i, but i then increments — skipping it. Fix: decrement i after removal, or iterate backward.

Question 38Output Trace

What is printed?

int[][] grid = {{1,2,3},{4,5,6},{7,8,9}};
int total = 0;
for (int r = 0; r < grid.length; r++) {
    total += grid[r][r];
}
System.out.println(total);

A.12 B.45 C.15 D.6

Correct Answer: C. Sums the main diagonal: grid[0][0]=1, grid[1][1]=5, grid[2][2]=9. Total = 15.

Question 39I / II / III

Which correctly describe differences between arrays and ArrayLists?

Arrays have a fixed size; ArrayLists can grow and shrink dynamically.
Arrays can hold primitive types; ArrayLists require wrapper classes such as Integer.
ArrayLists are faster than arrays when accessing elements by index.

A.I only B.I and II only C.II and III only D.I, II, and III

Correct Answer: B. I and II are true AP exam distinctions. III is false — array index access is generally faster due to no boxing overhead.

Question 40Output Trace

What is the final content of the ArrayList?

ArrayList list = new ArrayList<>();
list.add(10);
list.add(20);
list.add(30);
list.add(0, 5);
list.set(2, 25);
list.remove(3);

A.[5, 10, 25, 30] B.[5, 10, 25] C.[10, 20, 25] D.[5, 10, 20, 25]

Correct Answer: B. After 3 adds: [10,20,30]. add(0,5): [5,10,20,30]. set(2,25): [5,10,25,30]. remove(3): [5,10,25].

Question 41Error Spotting

This method counts elements equal to a target in a 2D array. What is the error?

public static int countTarget(int[][] matrix, int target) {
    int count = 0;
    for (int r = 0; r < matrix.length; r++) {
        for (int c = 0; c < matrix.length; c++) {
            if (matrix[r][c] == target) {
                count++;
            }
        }
    }
    return count;
}

A.count should be initialized to -1 to handle the no-match case. B.The inner loop uses matrix.length (row count) instead of matrix[r].length (column count), failing on non-square matrices. C.== cannot compare integers in Java; use .equals(). D.Indexed loops are incompatible with 2D arrays; an enhanced for loop is required.

Correct Answer: B. matrix.length gives the number of rows. For non-square matrices the column count is matrix[r].length. Using row count for columns causes ArrayIndexOutOfBoundsException on wider matrices.

Question 42I / II / III

Given: int[] arr = {8, 3, 5, 3, 8}; Which statements are TRUE?

arr.length returns 5
arr[arr.length - 1] returns 8
arr[5] returns 0 because it is beyond the last initialized element

A.I only B.I and II only C.II and III only D.I, II, and III

Correct Answer: B. I: arr.length=5 true. II: arr[4]=8 true. III: arr[5] throws ArrayIndexOutOfBoundsException — does NOT return 0.

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