AP CSA Unit 3 Practice Exam | 50 Free Questions

Question 1

What is printed?

int[] arr = new int[5];
System.out.println(arr[0]);

A) 0
B) null
C) 5
D) ArrayIndexOutOfBoundsException

Question 2

What is printed?

int[] arr = {10, 20, 30, 40, 50};
System.out.println(arr.length);

A) 4
B) 5
C) 50
D) Compile error - length is a method

Question 3

What is printed?

int[] arr = {10, 20, 30, 40, 50};
System.out.println(arr[5]);

A) 50
B) 0
C) ArrayIndexOutOfBoundsException
D) null

Question 4

What is printed?

String[] names = new String[3];
System.out.println(names[0]);

A) ""
B) null
C) 0
D) NullPointerException

Question 5

Which correctly creates an array with values 1, 2, 3?

A) int[] arr = new int[]{1, 2, 3};
B) int[] arr = {1, 2, 3};
C) int arr[] = {1, 2, 3};
D) All of the above

Question 6

What is printed?

int[] arr = {5, 10, 15, 20};
arr[2] = arr[0] + arr[1];
System.out.println(arr[2]);

A) 15
B) 25
C) 10
D) 30

Question 7

What is printed?

int[] a = {1, 2, 3};
int[] b = a;
b[0] = 99;
System.out.println(a[0]);

A) 1
B) 99
C) 0
D) Compile error

Question 8

What is printed?

double[] vals = {1.5, 2.5, 3.5};
System.out.println(vals[vals.length - 1]);

A) 1.5
B) 2.5
C) 3.5
D) ArrayIndexOutOfBoundsException

Question 9

Can you change the size of an array after it is created?

A) Yes, using arr.resize()
B) Yes, using arr.length = newSize
C) No, arrays have fixed size
D) Yes, by adding elements

Question 10

What is printed?

boolean[] flags = new boolean[3];
System.out.println(flags[0] + " " + flags[1] + " " + flags[2]);

A) true true true
B) false false false
C) null null null
D) 0 0 0

Question 11

What is printed?

int[] arr = {10, 20, 30};
System.out.println(arr);

A) [10, 20, 30]
B) 10 20 30
C) Something like [I@1a2b3c4
D) {10, 20, 30}

Question 12

What is the valid index range for an array of size n?

A) 1 to n
B) 0 to n
C) 0 to n-1
D) 1 to n-1

Question 13

What is printed?

int[] arr = {2, 4, 6, 8, 10};
int sum = 0;
for (int i = 0; i < arr.length; i++) {
    sum += arr[i];
}
System.out.println(sum);

A) 20
B) 30
C) 10
D) 5

Question 14

What is printed?

int[] arr = {5, 2, 8, 1, 9};
int max = arr[0];
for (int i = 1; i < arr.length; i++) {
    if (arr[i] > max) {
        max = arr[i];
    }
}
System.out.println(max);

A) 5
B) 1
C) 9
D) 8

Question 15

What is printed?

int[] arr = {1, 2, 3, 4, 5};
for (int num : arr) {
    num = num * 2;
}
System.out.println(arr[0] + " " + arr[4]);

A) 2 10
B) 1 5
C) 1 10
D) 2 5

Question 16

What is printed?

int[] arr = {1, 2, 3, 4, 5};
for (int i = 0; i < arr.length; i++) {
    arr[i] = arr[i] * 2;
}
System.out.println(arr[0] + " " + arr[4]);

A) 1 5
B) 2 10
C) 1 10
D) 2 5

Question 17

What is printed?

int[] arr = {3, 7, 2, 9, 4};
int count = 0;
for (int num : arr) {
    if (num > 5) {
        count++;
    }
}
System.out.println(count);

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

Question 18

What is printed?

int[] arr = {1, 2, 3, 4, 5};
for (int i = arr.length - 1; i >= 0; i--) {
    System.out.print(arr[i] + " ");
}

A) 1 2 3 4 5
B) 5 4 3 2 1
C) 5 4 3 2
D) ArrayIndexOutOfBoundsException

Question 19

What is printed?

int[] arr = {10, 20, 30, 40, 50};
int target = 30;
int index = -1;
for (int i = 0; i < arr.length; i++) {
    if (arr[i] == target) {
        index = i;
        break;
    }
}
System.out.println(index);

A) -1
B) 2
C) 30
D) 3

Question 20

What is printed after this code runs?

int[] arr = {1, 2, 3, 4, 5};
int temp = arr[0];
arr[0] = arr[4];
arr[4] = temp;
System.out.println(arr[0] + " " + arr[4]);

A) 1 5
B) 5 1
C) 5 5
D) 1 1

Question 21

What does this code do?

for (int i = 0; i < arr.length / 2; i++) {
    int temp = arr[i];
    arr[i] = arr[arr.length - 1 - i];
    arr[arr.length - 1 - i] = temp;
}

A) Sorts the array
B) Reverses the array
C) Doubles each element
D) Shifts elements left

Question 22

What is printed?

int[] arr = {1, 2, 3, 4, 5};
int first = arr[0];
for (int i = 0; i < arr.length - 1; i++) {
    arr[i] = arr[i + 1];
}
arr[arr.length - 1] = first;
System.out.println(arr[0] + " " + arr[4]);

A) 1 5
B) 2 1
C) 5 1
D) 2 5

Question 23

What is the time complexity of linear search?

A) O(1)
B) O(log n)
C) O(n)
D) O(n²)

Question 24

What is printed?

int[] arr = {1, 2, 2, 3, 3, 3};
int count = 1;
int maxCount = 1;
for (int i = 1; i < arr.length; i++) {
    if (arr[i] == arr[i-1]) {
        count++;
        if (count > maxCount) {
            maxCount = count;
        }
    } else {
        count = 1;
    }
}
System.out.println(maxCount);

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

Question 25

What is printed?

int[] arr = {1, 2, 3, 4, 5};
double avg = 0;
for (int num : arr) {
    avg += num;
}
avg = avg / arr.length;
System.out.println(avg);

A) 3
B) 3.0
C) 15.0
D) 2.5

Question 26

Which correctly declares an ArrayList of Strings?

A) ArrayList<String> list = new ArrayList<String>();
B) ArrayList<String> list = new ArrayList<>();
C) List<String> list = new ArrayList<>();
D) All of the above

Question 27

What is printed?

ArrayList<Integer> list = new ArrayList<>();
list.add(10);
list.add(20);
list.add(30);
System.out.println(list.size());

A) 2
B) 3
C) 30
D) Compile error

Question 28

What is printed?

ArrayList<String> list = new ArrayList<>();
list.add("A");
list.add("B");
list.add("C");
System.out.println(list.get(1));

A) A
B) B
C) C
D) 1

Question 29

What is printed?

ArrayList<Integer> list = new ArrayList<>();
list.add(10);
list.add(20);
list.add(30);
list.set(1, 99);
System.out.println(list);

A) [10, 20, 30]
B) [10, 99, 30]
C) [99, 20, 30]
D) [10, 20, 99]

Question 30

What is printed?

ArrayList<String> list = new ArrayList<>();
list.add("A");
list.add("B");
list.add("C");
list.remove(1);
System.out.println(list);

A) [A, B, C]
B) [A, C]
C) [B, C]
D) [A, B]

Question 31

What is printed?

ArrayList<Integer> list = new ArrayList<>();
list.add(10);
list.add(20);
list.add(1, 15);
System.out.println(list);

A) [10, 20, 15]
B) [10, 15, 20]
C) [15, 10, 20]
D) [10, 15]

Question 32

What is the difference between arrays and ArrayList?

A) Arrays can grow, ArrayList cannot
B) ArrayList can store primitives directly
C) ArrayList can grow/shrink, arrays have fixed size
D) Arrays use methods, ArrayList uses []

Question 33

Why can't you use ArrayList<int>?

A) int is too small
B) Generics require reference types, not primitives
C) ArrayList only works with Strings
D) You can use ArrayList<int>

Question 34

What is printed?

ArrayList<Integer> list = new ArrayList<>();
list.add(5);
list.add(10);
list.add(15);
for (int i = 0; i < list.size(); i++) {
    list.remove(i);
}
System.out.println(list);

A) []
B) [10]
C) [5, 15]
D) IndexOutOfBoundsException

Question 35

What is the correct way to remove all elements while traversing?

A) Traverse forward and remove
B) Traverse backward and remove
C) Use enhanced for loop and remove
D) You cannot remove while traversing

Question 36

What is printed?

ArrayList<String> list = new ArrayList<>();
list.add("cat");
list.add("dog");
list.add("cat");
System.out.println(list.indexOf("cat") + " " + list.lastIndexOf("cat"));

A) 0 0
B) 0 2
C) 2 2
D) -1 -1

Question 37

What is printed?

ArrayList<Integer> list = new ArrayList<>();
list.add(1);
list.add(2);
list.add(3);
list.clear();
System.out.println(list.size() + " " + list.isEmpty());

A) 0 true
B) 3 false
C) 0 false
D) null true

Question 38

What is printed?

ArrayList<Integer> list = new ArrayList<>();
list.add(10);
list.add(20);
list.add(30);
int sum = 0;
for (Integer num : list) {
    sum += num;
}
System.out.println(sum);

A) 30
B) 60
C) 3
D) Compile error

Question 39

What is printed?

ArrayList<Integer> list = new ArrayList<>();
list.add(5);
list.add(3);
list.add(8);
list.add(1);
int min = list.get(0);
for (int i = 1; i < list.size(); i++) {
    if (list.get(i) < min) {
        min = list.get(i);
    }
}
System.out.println(min);

A) 5
B) 1
C) 8
D) 3

Question 40

What is printed?

ArrayList<String> list = new ArrayList<>();
list.add("A");
list.add("B");
list.add("C");
for (int i = list.size() - 1; i >= 0; i--) {
    System.out.print(list.get(i));
}

A) ABC
B) CBA
C) BCA
D) ACB

Question 41

What is printed?

ArrayList<Integer> list = new ArrayList<>();
list.add(1);
list.add(2);
list.add(3);
list.add(4);
list.add(5);
for (int i = list.size() - 1; i >= 0; i--) {
    if (list.get(i) % 2 == 0) {
        list.remove(i);
    }
}
System.out.println(list);

A) [1, 3, 5]
B) [2, 4]
C) [1, 2, 3, 4, 5]
D) IndexOutOfBoundsException

Question 42

What happens with this code?

ArrayList<String> list = new ArrayList<>();
list.add("A");
list.add("B");
list.add("C");
for (String s : list) {
    if (s.equals("B")) {
        list.remove(s);
    }
}

A) Removes "B" successfully
B) ConcurrentModificationException
C) Nothing happens
D) Compile error

Question 43

What is printed?

ArrayList<Integer> list = new ArrayList<>();
list.add(10);
list.add(20);
list.add(30);
System.out.println(list.contains(20) + " " + list.contains(25));

A) true true
B) true false
C) false true
D) 1 -1

Question 44

What is printed?

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

A) 10 [5, 15]
B) 5 [10, 15]
C) 1 [5, 10, 15]
D) null [5, 15]

Question 45

What is the difference between remove(int index) and remove(Object obj)?

A) No difference
B) remove(int) removes by position, remove(Object) removes by value
C) remove(Object) is faster
D) remove(int) only works with Integers

Question 46

What is printed?

ArrayList<Integer> nums = new ArrayList<>();
nums.add(3);
nums.add(1);
nums.add(4);
nums.add(1);
nums.add(5);
int count = 0;
for (Integer n : nums) {
    if (n == 1) count++;
}
System.out.println(count);

A) 1
B) 2
C) 5
D) 0

Question 47

What is printed?

ArrayList<String> words = new ArrayList<>();
words.add("apple");
words.add("banana");
words.add("cherry");
String longest = words.get(0);
for (String w : words) {
    if (w.length() > longest.length()) {
        longest = w;
    }
}
System.out.println(longest);

A) apple
B) banana
C) cherry
D) 6

Question 48

What is printed?

ArrayList<Integer> list = new ArrayList<>();
for (int i = 1; i <= 5; i++) {
    list.add(i * 10);
}
list.add(2, 25);
System.out.println(list.get(3));

A) 25
B) 30
C) 40
D) 20

Question 49

What is printed?

ArrayList<Integer> a = new ArrayList<>();
ArrayList<Integer> b = new ArrayList<>();
a.add(1);
a.add(2);
b.add(1);
b.add(2);
System.out.println(a == b);
System.out.println(a.equals(b));

A) true, true
B) false, true
C) false, false
D) true, false

Question 50

What is printed?

ArrayList<Integer> list = new ArrayList<>();
list.add(10);
list.add(20);
list.add(30);
for (int i = 0; i < list.size(); i++) {
    list.set(i, list.get(i) + 5);
}
System.out.println(list);

A) [10, 20, 30]
B) [15, 25, 35]
C) [15, 20, 30]
D) ConcurrentModificationException

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Unit 3 Practice Exam: Arrays & ArrayList

Unit 3: Arrays & ArrayList

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