1Z0-811 Practice Test 14 — 15 Questions

Question 1

Arrange the steps to use a for loop to iterate over an array in Java in the correct order.

Accepted Answer

1. Declare and initialize the array. 2. Write a for loop with initialization, condition, and increment statements. 3. Access elements using array[index] inside the loop. 4. Execute desired operations on each element.. First set up the array, then write a for loop with proper syntax, access elements using index, execute body, and consider enhanced for.

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1. Write a for loop header with initialization, condition, and increment. 2. Declare and initialize the array inside the loop. 3. Access elements using array[index]. 4. Perform operations.

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1. Access array elements using index. 2. Declare and initialize the array. 3. Write a for loop to iterate. 4. Perform operations.

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1. Declare and initialize the array. 2. Perform operations on array elements without a loop. 3. Write a for loop later. 4. Access elements using index.

Question 2

A developer tries to compile a modular Java application using the command shown in the exhibit. The compilation fails with the error shown. What is the most likely cause?

Accepted Answer

The `--module-source-path` does not include the location of the utility module.. The error indicates that the compiler cannot find the utility module referenced in the `requires` directive. The `--module-source-path` option must list all directories containing module source code. Since the utility module's source is not included in the specified path, the compilation fails. Option D correctly identifies this missing path as the cause.

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The `-d out` flag is incorrectly specified; it should point to the source directory.

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The `-m` option should be `--module` instead.

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The import statement should use the fully qualified class name instead of importing.

Question 3

A developer is using try-with-resources with a custom resource class that implements AutoCloseable. The class's close() method throws a custom exception `ResourceException`. In the try block, an IOException occurs. Which of the following best describes the exception that is propagated to the caller?

Accepted Answer

The IOException is propagated with the ResourceException added as a suppressed exception.. When using try-with-resources, if both the try block and the close() method throw exceptions, the exception from the try block is the one propagated to the caller, and any exception from close() is added as a suppressed exception to that primary exception. This is specified in Java's try-with-resources semantics (JLS §14.20.3). Therefore, the IOException from the try block is propagated, and the ResourceException from close() is suppressed within it.

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The IOException is discarded and the ResourceException is thrown.

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The IOException is lost and the caller receives no exception.

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Both exceptions are thrown simultaneously as a multi-exception.

Question 4

A developer writes: Object obj = new String("Hello"); System.out.println(obj.length()); What will be the output?

Accepted Answer

Compilation error. The code fails to compile because the reference variable 'obj' is of type Object, which does not have a length() method. The length() method is defined in the String class, not in Object. Since the compiler checks the declared type (Object) for method availability, it does not find length() and produces a compilation error.

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null

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Runtime exception

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5

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0

Question 5

A class has a static variable counter initialized to 0. Two threads increment counter 1000 times each using counter++. What is a possible final value of counter?

Accepted Answer

Any value between 1000 and 2000 inclusive. `counter++` is not an atomic operation; it consists of three steps: read, increment, and write. When two threads execute this non-atomic operation concurrently without synchronization, interleaving can cause lost updates, resulting in a final value that is less than 2000 but at least 1000 (since each thread increments at least once). The possible final value is any integer between 1000 and 2000 inclusive.

Answer

1000

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0

Answer

2000

Question 6

A class defines two methods with the same name but different parameter lists. This is known as:

Accepted Answer

Method overloading. Method overloading occurs when a class defines multiple methods with the same name but different parameter lists (different number, type, or order of parameters). This is a compile-time polymorphism mechanism in Java that allows a method to handle different inputs without changing its name.

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Method overriding

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Method hiding

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Method shadowing

Question 7

A method is designed to compute the average of an array of test scores. What should the method return if the array is empty (length 0)?

Accepted Answer

Return 0.0. The method should return 0.0 for an empty array to avoid division by zero and to provide a safe default value. In Java, an empty array has length 0, and computing the average would require dividing by zero, which throws an ArithmeticException. Returning 0.0 is a common convention for empty collections, as it allows the caller to handle the result gracefully without crashing.

Answer

Do not compile; requires a return of type double

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Throw a RuntimeException

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Return null

Question 8

What is the result of the following code snippet? int a = 5; int b = 2; double c = (double) (a / b); System.out.println(c);

Accepted Answer

2.0. The expression `(a / b)` performs integer division, resulting in 2 (since both a and b are ints). The cast `(double)` is applied to the result of that integer division, converting the integer 2 to 2.0. The output is therefore 2.0.

Answer

2

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Compilation error

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2.5

Question 9

A method 'public static double average(int[] numbers) { int sum = 0; for (int i = 0; i < numbers.length; i++) sum += numbers[i]; return sum / numbers.length; }' is called with array {10, 20, 30}. What change is needed to return the correct average?

Accepted Answer

Change 'sum / numbers.length' to '(double) sum / numbers.length'. The method performs integer division because both `sum` (int) and `numbers.length` (int) are integers, truncating the fractional part. Casting `sum` to `double` before division forces floating-point arithmetic, preserving the decimal value. For the array {10, 20, 30}, the correct average is 20.0, but integer division yields 20 (truncated from 20.0, though here it matches by coincidence; for non-integer averages like {10, 20, 31}, the error would be obvious).

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Change the loop to for (int i = 1; i <= numbers.length; i++)

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Change return type to int

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Add a second parameter for the length

Question 10

A developer is working on a Java application that processes user input. The application reads an integer from the command line using args[0], converts it to an int, and uses it in a loop. When testing, the application throws a NumberFormatException when the user provides an alphabetic string. The developer needs to handle this exception gracefully by prompting the user to enter a valid number and retrying. However, the developer must avoid infinite loops. The current code uses a while loop with a flag. Which approach ensures the code handles the exception, provides feedback, and terminates if the user enters 'quit'? The environment is a standard Java SE 11 application. The developer wants a robust solution without using external libraries.

Accepted Answer

Use a try-catch inside a loop that continues if exception caught, and breaks if input equals 'quit' or conversion succeeds.. It uses a try-catch inside a while loop that continues if an exception is caught, allowing the user to re-enter input. The loop also checks if the input equals 'quit' to break out, ensuring the program can terminate gracefully. This approach provides feedback (prompting the user) and avoids infinite loops. Option B is incorrect because ignoring the exception would not provide feedback or allow retry. Option C is incorrect because it never checks for 'quit', risking an infinite loop. Option D is incorrect because calling System.exit(0) terminates the program abruptly, which is not graceful.

Answer

Catch the exception and ignore it; the loop will naturally terminate.

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Use a do-while loop that never checks for 'quit'; the exception is caught outside the loop.

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Catch the exception in the loop and call System.exit(0) immediately.

Question 11

A developer is writing a Java application that processes a large number of transactions. The application must ensure that each transaction is committed only if all steps complete successfully, otherwise the entire transaction should be rolled back. Which Java concept should the developer use to implement this requirement?

Accepted Answer

Exception handling. Exception handling in Java allows the developer to catch runtime failures (e.g., SQLException, IOException) within a try block and, in the catch block, invoke a rollback on the transaction (e.g., Connection.rollback()). If all steps succeed, the transaction is committed via Connection.commit(). This ensures atomicity — the 'all-or-nothing' property required for transaction processing.

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Inheritance

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Multithreading

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Encapsulation

Question 12

Which TWO statements are correct about array declaration and initialization in Java?

Accepted Answer

int[] a = new int[5];. `int[] a = new int[5];` declares an array of integers with a size of 5 and initializes all elements to their default value (0 for int). This is the standard syntax for array declaration and initialization in Java, where the size is specified after `new`.

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int a[5];

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int a[5] = new int[5];

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int[] a = new int[5] {1,2,3,4,5};

Question 13

Arrange the steps to implement an interface in a Java class in the correct order.

Accepted Answer

Define the interface, then create a class that implements it, then implement all abstract methods, then add extra methods, then use the class. First define the interface, then create a class that implements it, implement all abstract methods, add extra methods, and then use the class.

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Create a class that implements the interface, then define the interface, then implement all abstract methods, then add extra methods, then use the class

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Implement all abstract methods, then define the interface, then create a class that implements it, then add extra methods, then use the class

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Use the class, then define the interface, then create a class that implements it, then implement all abstract methods, then add extra methods

Question 14

Match each Java keyword to its use.

Accepted Answer

static: Belongs to the class rather than instances. Keywords in Java have specific meanings. Static members are class-level, final prevents modification, abstract requires subclassing, and synchronized controls thread access. Distractors confuse static with final.

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static: Declares a method that cannot be overridden

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final: Belongs to the class rather than instances

Question 15

Match each OOP concept to its Java implementation.

Accepted Answer

Encapsulation: Use of private fields with public getter and setter methods. Correct matches: Encapsulation with private fields/getters; Inheritance with extends; Polymorphism with method overriding. Common confusions include mixing abstraction and polymorphism.

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Polymorphism: abstract class and interface

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Abstraction: Method overriding

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Inheritance: Use of private fields