1Z0-811 Practice Test 2 — 10 Questions

Question 1

Which of the following is not a valid array variable declaration in Java?

Accepted Answer

int arr;. `int arr;` declares a simple integer variable, not an array. In Java, an array variable declaration must include square brackets ([]) to indicate the variable is an array type. Without brackets, the variable is a primitive or reference type, not an array.

Answer

int[] arr[];

Answer

int[] arr;

Answer

int arr[];

Question 2

Which TWO of the following are legal ways to declare and initialize an array?

Accepted Answer

int[] arr = new int[]{1,2,3};. It uses the valid syntax `int[] arr = new int[]{1,2,3};` which declares an array variable of type `int[]`, creates a new array object with an initializer list, and assigns it to the variable. This is a legal way to both declare and initialize an array in a single statement, as the array size is inferred from the number of elements in the initializer.

Answer

int arr = {1,2,3};

Answer

int arr[];

Answer

int[3] arr;

Question 3

Which THREE statements are true about the Java logging API (java.util.logging)?

Accepted Answer

Handlers can be attached to loggers to output messages. The Java Logging API allows Handlers (such as ConsoleHandler, FileHandler, or custom handlers) to be attached to Logger objects to output log messages to destinations like the console, files, or network sockets. This is a core design pattern of the API: loggers produce log records, and handlers are responsible for publishing them.

Answer

The default configuration logs all messages at FINEST level

Answer

All loggers automatically forward messages to the root logger

Question 4

A developer writes the following code: if (score >= 90) { grade = 'A'; } else if (score >= 80) { grade = 'B'; } else if (score >= 70) { grade = 'C'; } else { grade = 'D'; } What is the value of grade if score is 75?

Accepted Answer

'C'. The code uses a cascading if-else-if structure that evaluates conditions from top to bottom. When score is 75, the first condition (score >= 90) is false, the second (score >= 80) is false, and the third (score >= 70) is true, so grade is assigned 'C'. The else block is only reached if all prior conditions are false.

Answer

'B'

Answer

'D'

Answer

'A'

Question 5

You are tuning a real-time data processing application that reads sensor data from a queue. The system must process each sensor reading, but occasionally a reading is invalid (null) and should be skipped. The loop must run indefinitely until the application is shut down gracefully. The current implementation uses a while(true) loop with a break condition when a shutdown flag is set. However, the loop is consuming excessive CPU because it continuously polls the queue even when no data is available. You need to modify the loop to reduce CPU usage while still processing data efficiently. Which approach should you take?

Accepted Answer

Replace the polling mechanism with a blocking queue that blocks until data is available.. Using a blocking queue (e.g., `BlockingQueue.take()`) causes the consumer thread to block automatically until data becomes available, eliminating busy-waiting and drastically reducing CPU usage. This is the standard pattern for producer-consumer scenarios in Java, as it leverages the underlying `notify`/`wait` mechanism to avoid polling overhead.

Answer

Change the while(true) loop to a for loop that iterates a fixed number of times.

Answer

Add a Thread.sleep(100) inside the loop to reduce polling frequency.

Answer

Use a do-while loop with a Thread.yield() call to give other threads CPU time.

Question 6

A banking application uses a method to calculate interest: double calculateInterest(double balance) { return balance * 0.05; }. The method is called with an int argument: int accountBalance = 1000; double interest = calculateInterest(accountBalance); System.out.println(interest); The output is 50.0, but the expected output is 50.0. However, the developer notices that if the method is changed to return int, the output becomes 50.0 as well. Which statement about implicit casting is true?

Accepted Answer

The int argument is implicitly cast to double.. When a method expecting a `double` parameter is called with an `int` argument, Java performs implicit widening primitive conversion (casting) from `int` to `double`. This is safe because `double` can represent all `int` values without loss of precision. The `int` value 1000 is automatically converted to `1000.0` before being used in the calculation.

Answer

The double result is implicitly cast to int.

Answer

The code fails to compile because of type mismatch.

Answer

The multiplication result is automatically rounded.

Question 7

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

Accepted Answer

$test. ($test) is a valid Java identifier because identifiers can begin with a dollar sign ($) or an underscore (_), followed by any combination of letters, digits, dollar signs, or underscores. The Java Language Specification (JLS §3.8) explicitly allows the dollar sign as a starting character, though it is conventionally reserved for mechanically generated names.

Answer

class

Answer

my-var

Answer

2ndVar

Question 8

What is the output of: System.out.println(new Manager("Alice", 5).getName());

Accepted Answer

Alice. The code creates a new Manager object with the name "Alice" and a level of 5, then calls getName() on it. Assuming Manager extends a class (likely Employee) that has a constructor setting the name field via super(name), getName() returns the stored name "Alice". The code compiles and runs without exception, printing "Alice".

Answer

Runtime exception

Answer

Compilation fails

Answer

null

Question 9

Given: double d = 5.0; int i = d; What is the result?

Accepted Answer

Compilation fails. In Java, assigning a double to an int without an explicit cast causes a compilation error because double is a 64-bit floating-point type and int is a 32-bit integer type. Java does not allow implicit narrowing conversions due to potential loss of precision, so the code fails to compile.

Answer

5.0

Answer

5

Answer

Runtime error

Question 10

What is the scope of a variable declared inside a for loop?

Accepted Answer

Only inside the loop block. In Java, a variable declared inside a for loop (including the initialization block or the loop body) has block scope, meaning it is only accessible within the loop block itself. This is defined by the Java Language Specification (JLS §6.10), which states that the scope of a local variable declaration is the rest of the block in which the declaration appears. Once the loop completes, the variable goes out of scope and cannot be referenced.

Answer

Inside the package

Answer

Inside the class

Answer

Inside the entire method