Common array operations in Java - Practice Problems & Coding Challenges

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Challenge - 5 Problems

💻 code output

intermediate

Output of array sum calculation

What is the output of this Java code that sums all elements in an integer array?

Java

int[] numbers = {2, 4, 6, 8};
int sum = 0;
for (int num : numbers) {
    sum += num;
}
System.out.println(sum);

A 30

B 24

C SyntaxError

D 20

💻 code output

intermediate

Output of array reverse print

What does this Java code print when it prints the array elements in reverse order?

Java

int[] arr = {1, 3, 5, 7};
for (int i = arr.length - 1; i >= 0; i--) {
    System.out.print(arr[i] + " ");
}

A 7 5 3 1

B 1 3 5 7

C 7 5 3

D RuntimeError

💻 code output

advanced

Output of array element replacement

What is the output after replacing all negative numbers with zero in this array?

Java

int[] data = {4, -1, 7, -3, 0};
for (int i = 0; i < data.length; i++) {
    if (data[i] < 0) {
        data[i] = 0;
    }
}
for (int num : data) {
    System.out.print(num + " ");
}

A SyntaxError

B 4 0 7 0 0

C 4 0 7 -3 0

D 4 -1 7 -3 0

💻 code output

advanced

Output of array copy with System.arraycopy

What is the output of this code that copies part of one array into another?

Java

int[] source = {10, 20, 30, 40, 50};
int[] dest = {1, 2, 3, 4, 5};
System.arraycopy(source, 1, dest, 2, 2);
for (int i : dest) {
    System.out.print(i + " ");
}

A 1 2 20 30 5

B 10 20 30 40 50

C 1 2 10 20 5

D ArrayIndexOutOfBoundsException

🧠 conceptual

expert

Error type when accessing invalid array index

What error does this Java code produce when trying to access an invalid index in an array?

Java

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

A SyntaxError

B NullPointerException

C ArrayIndexOutOfBoundsException

D ClassCastException