1Z0-811 Java Basics and Syntax Practice Test 2 — 15 Questions

Question 1

Which access modifier makes a member visible only within its own class?

Accepted Answer

private. The private access modifier restricts visibility to only the class in which the member is declared. No other class, including subclasses or classes in the same package, can access a private member directly. This is the most restrictive access level in Java.

Answer

public

Answer

default (no modifier)

Answer

protected

Question 2

What is the result of the expression 10 % 3?

Accepted Answer

1. The modulo operator (%) in Java returns the remainder of the division of the left operand by the right operand. Since 10 divided by 3 equals 3 with a remainder of 1, the expression 10 % 3 evaluates to 1.

Answer

3.33

Answer

0

Answer

3

Question 3

Which TWO are valid identifiers in Java? (Choose two.)

Accepted Answer

$money. In Java, identifiers can begin with a letter, an underscore (_), or a dollar sign ($). The dollar sign is a valid starting character, so '$money' is a legal identifier. This is specified in the Java Language Specification (JLS §3.8).

Answer

123abc

Answer

2ndPlace

Answer

my-var

Question 4

Which THREE are valid ways to declare and initialize an integer variable in Java? (Choose three.)

Accepted Answer

int x = 1_000;. Java allows underscores in numeric literals (introduced in Java 7) to improve readability, and `1_000` is a valid integer literal representing 1000. The compiler simply ignores the underscores during parsing.

Answer

int x = 2.0;

Answer

int x = 0xG;

Question 5

Which TWO keywords are used for decision-making in Java? (Choose two.)

Accepted Answer

switch. The 'if' and 'switch' statements are both decision-making constructs in Java. 'if' evaluates a boolean expression to determine which block of code to execute, while 'switch' selects a block based on the value of an expression, typically an int, String, or enum. These are the two primary keywords for branching logic.

Answer

for

Answer

try

Answer

while

Question 6

What is the output of this program?

Accepted Answer

30
Sum: 1020. The code compiles and runs without error. The first line prints 30 because the loop variable 'i' ends up as 30 due to a bug in the loop logic. The second line prints 'Sum: 1020' because the variable 'sum' holds the value 10 (the loop only sums certain values incorrectly), and the expression 'Sum: ' + sum + '20' concatenates the string 'Sum: ', the integer 10, and the string '20' to produce 'Sum: 1020'. Therefore, option C is correct.

Answer

Runtime exception

Answer

Compilation error

Answer

30
Sum: 30

Question 7

What is the value printed?

Accepted Answer

2. The while loop condition is `x < 2`, so the loop executes while x is less than 2. Initially x=0. In the first iteration, x becomes 1; in the second, x becomes 2. After the second iteration, x=2, the condition `2 < 2` is false, so the loop stops. The code prints the value of x, which is 2 after the loop exits.

Answer

3

Answer

5

Answer

0

Question 8

What is the output?

```java
public class Test {
    public static void main(String[] args) {
        String s1 = "hello";
        String s2 = "hello";
        System.out.println(s1.equals(s2));
    }
}
```

Accepted Answer

True. The code compares two String objects 's1' and 's2' using the equals() method. Since both strings have the same content "hello", equals() returns true. The System.out.println statement then prints 'True'.

Answer

No output

Answer

Compilation error

Answer

False

Question 9

You are developing a Java application for a library management system. The system must track the number of books in each genre. You need to store genre names (String) and their counts (int). The data will be accessed frequently and modified rarely. Which Java data structure should you use to store this mapping efficiently, while ensuring that genre names are unique?

Accepted Answer

HashMap. HashMap is the correct choice because it stores key-value pairs, where each genre name (String) is a unique key mapped to its count (Integer). This provides O(1) average-time complexity for lookups and updates, which is ideal for frequent access and rare modifications. The HashMap ensures key uniqueness via its hash-based implementation, directly meeting the requirement of unique genre names.

Answer

ArrayList<Book>

Answer

LinkedList<String>

Answer

HashSet<String>

Question 10

You are writing a program that processes a list of transactions. Each transaction has a timestamp (long), amount (double), and type (String). The program needs to iterate through the transactions in the order they were added. Which collection should you use to maintain insertion order and allow fast iteration?

Accepted Answer

ArrayList<Transaction>. ArrayList maintains insertion order and provides O(1) random access and fast iteration via index-based traversal. It is the correct choice when you need to preserve the order in which elements were added and iterate over them sequentially without requiring sorting or unique constraints.

Answer

TreeSet<Transaction>

Answer

LinkedList<Transaction>

Answer

HashSet<Transaction>

Question 11

Arrange the steps to declare and initialize a one-dimensional array in Java in the correct order.

Accepted Answer

Step 1: Declare array variable (e.g., int[] arr;), Step 2: Allocate memory using new keyword (e.g., arr = new int[5];), Step 3: Assign values to elements (e.g., arr[0] = 1; arr[1] = 2; ...).. The process involves declaring the array variable, then assigning it a new array or initializer, and optionally providing initial values.

Answer

Step 1: Allocate memory using new keyword, Step 2: Declare array variable, Step 3: Assign values.

Answer

Step 1: Assign values to elements, Step 2: Declare array variable, Step 3: Allocate memory.

Answer

Step 1: Declare array variable, Step 2: Assign values to elements, Step 3: Allocate memory.

Question 12

Arrange the steps to use the Scanner class to read user input in Java in the correct order.

Accepted Answer

1. Import java.util.Scanner; 2. Create Scanner object: Scanner sc = new Scanner(System.in); 3. Prompt user: System.out.print("Enter value: "); 4. Read input: String input = sc.nextLine(); 5. Close scanner: sc.close();. First import Scanner, then create an instance, prompt user, read input, and finally close the scanner.

Answer

1. Create Scanner object: Scanner sc = new Scanner(System.in); 2. Import java.util.Scanner; 3. Prompt user: System.out.print("Enter value: "); 4. Read input: String input = sc.nextLine(); 5. Close scanner: sc.close();

Answer

1. Import java.util.Scanner; 2. Prompt user: System.out.print("Enter value: "); 3. Create Scanner object: Scanner sc = new Scanner(System.in); 4. Read input: String input = sc.nextLine(); 5. Close scanner: sc.close();

Answer

1. Import java.util.Scanner; 2. Create Scanner object: Scanner sc = new Scanner(System.in); 3. Read input: String input = sc.nextLine(); 4. Close scanner: sc.close(); 5. Prompt user: System.out.print("Enter value: ");

Question 13

Match each access modifier to its visibility level.

Accepted Answer

private: Visible only within the same class. In Java, access modifiers control visibility: private (class-only), default (package), protected (package + subclasses), public (everywhere). Common mistakes include confusing private with default and protected with private.

Answer

private: Visible within the same package

Answer

protected: Visible only within the same class

Question 14

Match each Java collection interface to its characteristics.

Accepted Answer

List: Ordered collection (also known as sequence) that allows duplicate elements.. List is ordered and allows duplicates; Set is unordered and no duplicates; Queue is FIFO order; Map maps keys to values with unique keys. Common confusions include swapping List/Set characteristics or misidentifying Map as a collection of single elements.

Answer

Set: Ordered collection that allows duplicate elements.

Answer

Map: Collection of elements with no order and no duplicates.

Question 15

A developer writes code to calculate the average of two integers: int a = 5; int b = 10; int avg = a / b;. Which change ensures the average is correctly calculated as a double?

Accepted Answer

Cast one operand to double: (double) a / b. In Java, when both operands of the division operator are integers, integer division is performed, truncating the fractional part. By casting one operand to double, the operation becomes floating-point division, yielding a double result (0.5). This ensures the average is calculated correctly as a double.

Answer

No change needed; integer division is correct

Answer

Change the variable types to double

Answer

Use Math.round(a / b)