1Z0-811 Practice Test 24 — 15 Questions

Question 1

Given the code snippet: int x = 5; int y = 2; double result = x / y; What is the value of result?

Accepted Answer

2.0. In Java, when both operands of the division operator are integers (int), integer division is performed, which truncates the fractional part. Here, x / y evaluates to 5 / 2 = 2 (integer division), and then the int value 2 is implicitly widened to double 2.0 when assigned to the double variable result.

Answer

Compilation fails

Answer

2.5

Answer

2

Question 2

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 3

Which THREE are valid Java identifiers?

Accepted Answer

my_value. (my_value) is a valid Java identifier because it starts with a letter (m) and contains only letters, digits, and underscores. Java identifiers must begin with a letter, underscore, or dollar sign, and subsequent characters can include letters, digits, underscores, or dollar signs.

Answer

2ndValue

Answer

my-var

Question 4

A developer encounters a ClassNotFoundException at runtime. The class is present in the source code and compiles fine. Which is the most likely cause?

Accepted Answer

The classpath does not include the directory or JAR containing the .class file.. A ClassNotFoundException occurs when the Java Virtual Machine (JVM) cannot locate the .class file for a referenced class at runtime, even though the source code compiled successfully. Since the class compiles fine, the issue is not with the source code but with the runtime environment — specifically, the classpath does not include the directory or JAR file that contains the compiled .class file. The JVM uses the classpath to search for class files during class loading, and if the path is missing, it throws ClassNotFoundException.

Answer

The class is in the wrong package.

Answer

The class is abstract.

Answer

The class has a static initializer that fails.

Question 5

What is the output if an ArithmeticException occurs in the try block and there is a finally block?

Accepted Answer

The finally block executes, then the method throws the exception.. In Java, the `finally` block always executes after the `try` block, regardless of whether an exception occurs. If an `ArithmeticException` is thrown in the `try` block, the `finally` block runs first, and then the exception propagates up the call stack to be handled by an appropriate exception handler or the default handler.

Answer

The exception is caught and handled by the finally block.

Answer

The finally block does not execute if an exception occurs.

Answer

The method exits immediately without executing finally.

Question 6

A developer says Java is platform-independent because of the JVM. Which statement best explains this?

Accepted Answer

Java source code is compiled into bytecode, which runs on the Java Virtual Machine (JVM).. Java source code is compiled into bytecode, which runs on the JVM, making it platform-independent at the source level. Option A is incorrect because Java does not compile to native code for each platform; it compiles to bytecode. Option C is incorrect because Java uses both a compiler and interpreter/JIT. Option D is incorrect because the JVM itself is platform-specific, but bytecode is not.

Answer

Java source code is compiled directly into native machine code for each platform.

Answer

The JVM is written in platform-independent code, allowing it to run anywhere.

Answer

Java uses an interpreter only, so the source code is interpreted directly on any platform.

Question 7

Which THREE statements are correct about the 'main' method signature in Java?

Accepted Answer

It must be declared public.. The Java Language Specification (JLS) requires the main method to be declared public so that the JVM can access it from outside the class. Without public visibility, the JVM would not be able to invoke the method as the entry point of the application.

Answer

It can be declared to return an int.

Answer

It can be named any valid identifier.

Question 8

Given the code snippet: double d = 10.5; int i = (int) d; System.out.println(i); What is the output?

Accepted Answer

10. Casting a double to int truncates the fractional part, so 10.5 becomes 10. Option A (10.0) is incorrect because the result is an int without decimals; Option B is the original value; Option D is incorrect because the code compiles and runs.

Answer

10.0

Answer

10.5

Answer

Compilation error

Question 9

Which statement about try-catch is true?

Accepted Answer

A catch block can only handle one type of exception.. In Java, a catch block is defined with a single exception type parameter, meaning it can only handle one specific type of exception (or its subclasses if the parameter is a superclass). This is enforced by the language syntax: `catch (ExceptionType e)` allows only one exception type per catch clause.

Answer

A finally block is always required.

Answer

A try block without a catch or finally is legal.

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A try block can have multiple catch blocks for the same exception type.

Question 10

You are maintaining a multi-threaded banking application that processes transactions. In the `processTransaction` method, you have a try-catch block that catches `Exception` to handle any unexpected errors. Recently, the application intermittently fails to update account balances correctly due to unhandled exceptions. The logs show that sometimes a `RuntimeException` is thrown from a nested method, but it is not being logged or handled properly, leading to inconsistent state. The team wants to improve the exception handling to ensure that all exceptions are caught, logged, and the transaction is rolled back properly. The method currently uses a primitive try-catch-finally where the finally block commits the transaction if no exception occurred. Which approach best addresses the issue while maintaining clarity and correctness?

Accepted Answer

Inside the try block, set a boolean success flag to true upon completion; in the finally block, check the flag: if false, rollback; if true, commit. Additionally, catch specific exceptions, log them, and ensure rollback logic is invoked.. Option C is correct because it uses a boolean success flag set inside the try block; the finally block checks the flag to commit only if success, and rolls back otherwise. This ensures the transaction is committed only when no exception occurred. Additionally, catching specific exceptions (including RuntimeException) and logging them provides proper error handling. Option A is wrong because removing the catch block eliminates the ability to log and handle exceptions specifically, even though a boolean flag in finally can manage the commit/rollback. Option B is wrong because even though it adds a catch for RuntimeException and calls rollback, the finally block still unconditionally commits afterward, which can override the rollback. Option D is wrong because declaring throws Exception pushes the rollback responsibility to the caller without resolving the local transaction consistency.

Answer

Remove the `catch (Exception e)` block and rely solely on the finally block to commit or roll back based on a boolean flag set in the try block.

Answer

Add a separate catch block for `RuntimeException` before the existing `catch (Exception e)` and call rollback there, then rethrow the exception.

Answer

Declare the method with `throws Exception` and let the caller handle the transaction rollback.

Question 11

A developer writes: String s = "Hello"; s.concat(" World"); System.out.println(s); What is the output?

Accepted Answer

Hello. Strings in Java are immutable. The `concat()` method returns a new string but does not modify the original string `s`. Since the return value is not assigned to any variable, the original string `s` remains unchanged, so `System.out.println(s)` prints "Hello".

Answer

Compilation fails

Answer

Hello World

Answer

Hello World

Question 12

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 13

A company manages employee data stored in an array of Employee objects. The HR application frequently needs to find an employee by ID. The current implementation uses a linear search through the array each time. Performance reports indicate that this search is becoming a bottleneck as the company grows. The array is not sorted, and the company does not want to sort it because the order is meaningful for display. The array is large and frequently updated. The development team considers several options to improve the search performance without changing the array order. Which approach should they implement?

Accepted Answer

Create a HashMap that maps IDs to Employee objects, and maintain it alongside the array.. The best choice because using a HashMap provides O(1) average-time lookups, which is far superior to linear search. The HashMap can be maintained alongside the array without disturbing the array order, as updates to the array are reflected in the HashMap. Option B (parallel streams) still performs a linear search (O(n)) and adds overhead for parallelization, so it does not solve the bottleneck. Option C (HashSet of IDs) only allows checking existence but does not provide the Employee object; you would still need to search the array to retrieve the Employee, so it does not reduce complexity. Option D (binary search on a sorted copy) requires O(n log n) time to sort a copy for each search, which is even worse than linear search.

Answer

Use parallel streams to perform the search in parallel.

Answer

Convert the array to a HashSet of employee IDs and use contains() to check existence.

Answer

Use Arrays.binarySearch() on the array after temporarily sorting a copy each time.

Question 14

Refer to the exhibit. Given the code, what is the value printed to the console?

Accepted Answer

18. 18 (option C). The expression `a++ + --b * 2` is evaluated according to Java operator precedence: postfix increment (`a++`) uses the current value of `a` (10) then increments `a` to 11; prefix decrement (`--b`) decrements `b` from 5 to 4 then uses 4; multiplication has higher precedence than addition, so `--b * 2` computes 4 * 2 = 8; then addition: 10 + 8 = 18. Option A (19) would result if the postfix increment had been applied before the rest of the expression (i.e., using 11 instead of 10). Option B (21) would result if both increments were applied before evaluation (a becomes 11, b becomes 4, and then 11 + 4 * 2 = 11 + 8 = 19, not 21; actually 21 is far off). Option D (20) would result if addition were performed before multiplication (10 + 4 = 14, then 14 * 2 = 28, not 20; 20 is not directly derivable). Thus only step-by-step evaluation yields 18.

Answer

19

Answer

21

Answer

20

Question 15

Which statement about method overloading with array parameters is true?

Accepted Answer

A method with parameter int[] and another with parameter Integer[] are overloaded.. Method overloading requires methods to have the same name but different parameter lists. int[] and Integer[] are different parameter types (primitive array vs. wrapper class array), so they satisfy the overloading requirement. The return type is irrelevant for overloading.

Answer

A method with parameter int[] and another with parameter int... are overloaded.

Answer

Two methods with the same name and same parameter types but different return types are considered overloaded.

Answer

A method with parameter int[] and another with parameter int[][0] are overloaded.