AP Computer Science A Full-length practice exam 3 — Free with Answer Explanations

Question 1

What is the output of the following code?

ArrayList<Integer> list = new ArrayList<>();
list.add(5);
list.add(10);
list.add(15);
list.remove(1);
System.out.println(list);

A.[5, 15]B.[5, 10]C.[10, 15]D.[5, 10, 15]

Question 2

What is the state of array a after the following code executes?

int[][] a = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
int[] temp = a[0];
a[0] = a[2];
a[2] = temp;

A.Row 0: {1,2,3}, Row 2: {7,8,9} (unchanged)B.Row 0: {7,8,9}, Row 1: {4,5,6}, Row 2: {1,2,3}C.Row 0: {1,2,3}, Row 1: {8,5,2}, Row 2: {7,4,9}D.Row 0: {7,8,9}, Row 1: {1,2,3}, Row 2: {4,5,6}

Question 3

What is the value of count after the following code executes?

int count = 0;
for (int i = 0; i < 4; i++) {
    for (int j = 0; j < 3; j++) {
        count++;
    }
}

A.7B.12C.16D.10

Question 4

Consider the following code. What is the value of z?

int x = 7;
int y = 3;
double z = x / y + 0.5;

A.2.833...B.2.5C.2.0D.3.5

Question 5

What is the output of the following code?

String s = null;
System.out.println(s.length());

A.0B.NullPointerException at runtimeC.Compile errorD.null

Question 6

What is the output of the following code?

ArrayList<Integer> list = new ArrayList<>();
for (int i = 1; i <= 5; i++) {
    list.add(i);
}
for (int i = 0; i < list.size(); i++) {
    System.out.print(list.get(i) + " ");
}

A.1 2 3 4 5B.0 1 2 3 4C.1 2 3 4D.2 3 4 5 6

Question 7

What is the output of the following code?

int x = 10;
if (x++ > 10) {
    System.out.println("greater");
} else {
    System.out.println("not greater");
}
System.out.println(x);

A.greater\n11B.not greater\n11C.not greater\n10D.greater\n10

Question 8

What is printed by the following code?

public class Temp {
    private double celsius;
    
    public Temp(double c) { celsius = c; }
    
    public double toFahrenheit() {
        return celsius * 9 / 5 + 32;
    }
    
    public String toString() {
        return celsius + "C";
    }
}

// In main:
Temp t = new Temp(100);
System.out.println(t);
System.out.println(t.toFahrenheit());

A.Temp@[hashcode]\n212.0B.100.0C\n212.0C.100C\n212.0D.100.0C\n180.0

Question 9

Which expression is equivalent to !(a && b) according to De Morgan's Law?

A.!a && !bB.!a || !bC.a || bD.!(a) && !(b)

Question 10

Given the following code:

Animal a = new Dog();
if (a instanceof Dog) {
    System.out.println("Dog");
} else {
    System.out.println("Not Dog");
}

What is printed, assuming Dog extends Animal?

A.Not DogB.Compile error: cannot use instanceof with a parent type variableC.DogD.Runtime exception: ClassCastException

Question 11

What is the output of the following code?

String s = "coding";
int count = 0;
for (int i = 0; i < s.length(); i++) {
    if (s.charAt(i) == 'i' || s.charAt(i) == 'o') {
        count++;
    }
}
System.out.println(count);

A.1B.2C.3D.6

Question 12

Which of the following correctly declares a boolean variable and assigns it the result of a comparison?

// Option A
boolean result = (7 > 3);

// Option B
Boolean result = 7 > 3;

// Option C
bool result = 7 > 3;

// Option D
boolean result = "7 > 3";

A.Option A onlyB.Options A and BC.Option C onlyD.Option D only

Question 13

Consider the following method:

public static int power(int base, int exp) {
    if (exp == 0) return 1;
    return base * power(base, exp - 1);
}

How many times total is power called (including the initial call) when evaluating power(2, 4)?

A.4B.5C.8D.16

Question 14

What is the output of the following code?

int x = Integer.MAX_VALUE;
x = x + 1;
System.out.println(x > 0);

A.trueB.falseC.Compile errorD.Runtime exception

Question 15

A class declares public String toString(). Which statement is true about this method?

A.It overloads the Object class's toString() because all classes implicitly extend Object.B.It overrides Object's toString() and is called automatically by print methods and string concatenation.C.It must call super.toString() or a compile error occurs.D.It has no effect because Java does not use toString() automatically.

Question 16

Consider the following recursive method:

public static int sumArray(int[] arr, int index) {
    if (index == arr.length) return 0;
    return arr[index] + sumArray(arr, index + 1);
}

What is returned by sumArray(new int[]{3, 1, 4, 1, 5}, 0)?

A.3B.9C.14D.15

Question 17

What is the result of the following expression in Java?

int result = 3 + 4 * 2 - 10 / 4;

A.8B.9C.5D.12

Question 18

What is the output of the following code?

ArrayList<Integer> list = new ArrayList<>();
list.add(100);
list.add(200);
list.set(0, 999);
System.out.println(list.get(0));
System.out.println(list.size());

A.999\n2B.999\n3C.100\n2D.100\n3

Question 19

A student writes the following method to count elements equal to a target value in a 2D array:

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

For which input would this method produce incorrect results?

A.A 3×3 array with target 7B.A 1×1 array with target 0C.A jagged array where row 1 has more columns than row 0D.A 4×4 array with target -1

Question 20

Given the following classes:

public class Animal {
    public String speak() { return "..."; }
}
public class Dog extends Animal {
    public String speak() { return "Woof"; }
}

What does the following print?

Animal a = new Dog();
System.out.println(a.speak());

A....B.WoofC.Compile error: cannot assign Dog to Animal variableD....Woof

Question 21

What is the output of the following code?

int[] arr = {4, 2, 7, 1, 5};
for (int i = 0; i < arr.length - 1; i++) {
    if (arr[i] > arr[i + 1]) {
        int temp = arr[i];
        arr[i] = arr[i + 1];
        arr[i + 1] = temp;
    }
}
System.out.println(arr[0] + " " + arr[1]);

A.4 2B.2 4C.1 2D.2 1

Question 22

What does the following code print?

int a = 5;
int b = 5;
System.out.println(a == b);
String s1 = new String("hello");
String s2 = new String("hello");
System.out.println(s1 == s2);
System.out.println(s1.equals(s2));

A.true\ntrue\ntrueB.true\nfalse\ntrueC.true\nfalse\nfalseD.false\nfalse\ntrue

Question 23

What is the output of the following code?

public class Shape {
    public String describe() { return "Shape"; }
}
public class Circle extends Shape {
    public String describe() { return super.describe() + "-Circle"; }
}
// In main:
Circle c = new Circle();
System.out.println(c.describe());

A.ShapeB.CircleC.Shape-CircleD.Compile error: super.describe() is not allowed

Question 24

What is the value of result after the following code executes?

int[] arr = {2, 5, 3, 8, 1};
int result = 0;
for (int i = 0; i < arr.length; i++) {
    if (arr[i] % 2 == 0) {
        result++;
    }
}

A.1B.2C.3D.5

Question 25

What is the output of the following code?

import java.util.ArrayList;
ArrayList<Integer> list = new ArrayList<>();
list.add(10);
list.add(20);
list.add(30);
System.out.println(list.size());
System.out.println(list.get(1));

A.3\n20B.3\n10C.2\n20D.3\n30

Question 26

Which keyword is used to indicate that one class inherits from another in Java?

A.implementsB.inheritsC.extendsD.super

Question 27

What is the output of the following code?

int[][] g = new int[2][3];
for (int r = 0; r < g.length; r++) {
    for (int c = 0; c < g[r].length; c++) {
        g[r][c] = r + c;
    }
}
System.out.println(g[1][2]);

A.0B.2C.3D.5

Question 28

What is the output of the following code?

int[] arr = {5, 10, 15, 20};
System.out.println(arr.length);
System.out.println(arr[2]);

A.4\n15B.4\n20C.3\n15D.4\n10

Question 29

What is the state of list after the following code executes?

ArrayList<String> list = new ArrayList<>();
list.add("A");
list.add("B");
list.add("C");
list.add(1, "X");

A.[A, B, X, C]B.[A, X, B, C]C.[X, A, B, C]D.[A, B, C, X]

Question 30

What is the output of the following code?

ArrayList<String> list = new ArrayList<>();
list.add("apple");
list.add("banana");
list.add("cherry");
String result = "";
for (int i = list.size() - 1; i >= 0; i--) {
    result += list.get(i).charAt(0);
}
System.out.println(result);

A.abcB.cbaC.cherry banana appleD.cab

Question 31

Which of the following recursive methods contains a flaw that would cause infinite recursion for the call badRecurse(5)?

// Option A
public static int badRecurse(int n) {
    if (n == 0) return 0;
    return n + badRecurse(n + 1);
}

A.The base case n == 0 is never reached because each call increases n.B.The base case is missing entirely.C.The method returns the wrong type and will cause a compile error.D.The recursion is fine; badRecurse(5) returns a large positive number.

Question 32

What is the output of the following code?

public class Counter {
    private int count;
    
    public Counter(int start) {
        count = start;
    }
    
    public Counter add(int n) {
        count += n;
        return this;
    }
    
    public int getCount() { return count; }
}

// In main:
Counter c = new Counter(0);
System.out.println(c.add(3).add(4).getCount());

A.3B.7C.Compile error: add returns Counter, not void.D.4

Question 33

What is the output of the following code?

ArrayList<String> list = new ArrayList<>();
list.add("dog");
list.add("cat");
list.add("dog");
list.add("bird");
int count = 0;
for (String s : list) {
    if (s.equals("dog")) count++;
}
System.out.println(count);

A.1B.2C.3D.4

Question 34

What is the output of the following code?

int i = 1;
while (i < 16) {
    i *= 2;
}
System.out.println(i);

A.8B.16C.15D.32

Question 35

What is the output of the following code?

public class Accumulator {
    private static int total = 0;
    private int value;
    
    public Accumulator(int v) {
        value = v;
        total += v;
    }
    
    public static int getTotal() { return total; }
}

// In main:
Accumulator a1 = new Accumulator(10);
Accumulator a2 = new Accumulator(20);
Accumulator a3 = new Accumulator(5);
System.out.println(Accumulator.getTotal());

A.5B.35C.10D.0

Question 36

An abstract class Figure is defined as:

public abstract class Figure {
    public abstract double area();
    public void printArea() {
        System.out.println("Area: " + area());
    }
}

Which of the following statements is true?

A.new Figure() is valid because Figure has a concrete method.B.Any concrete subclass of Figure must provide an implementation of area().C.Abstract classes cannot have concrete methods like printArea().D.printArea() will not compile because area() has no implementation in Figure.

Question 37

Which of the following correctly compares two String objects for equal content in Java?

String a = "hello";
String b = "hello";

A.if (a == b)B.if (a.equals(b))C.if (a.compareTo(b) == true)D.if (String.equals(a, b))

Question 38

What is the output of the following code?

int[][] m = {{2, 4}, {6, 8}};
for (int r = 0; r < m.length; r++) {
    for (int c = 0; c < m[r].length; c++) {
        System.out.print(m[r][c] + " ");
    }
}

A.2 6 4 8B.2 4 6 8C.8 6 4 2D.4 8 2 6

Question 39

What is the value of result after this code executes?

double result = Math.sqrt(Math.pow(3.0, 2) + Math.pow(4.0, 2));

A.5.0B.7.0C.25.0D.12.5

Question 40

Which of the following correctly removes all elements equal to 0 from an ArrayList without skipping elements?

ArrayList<Integer> list = new ArrayList<>();
// list contains: [0, 5, 0, 3, 0]

A.java\nfor (int i = 0; i < list.size(); i++) {\n if (list.get(i) == 0) list.remove(i);\n}B.java\nfor (int i = list.size() - 1; i >= 0; i--) {\n if (list.get(i) == 0) list.remove(i);\n}C.java\nfor (int val : list) {\n if (val == 0) list.remove(val);\n}D.java\nlist.remove(0);