1Z0-811 Practice Test 9 — 10 Questions

Question 1

A method declares throws FileNotFoundException and SQLException. Which statement about the caller is true?

Accepted Answer

The caller must handle or declare both exceptions.. In Java, when a method declares checked exceptions (like FileNotFoundException and SQLException) in its throws clause, any caller must either handle each checked exception with a try-catch block or declare them in its own throws clause. The compiler enforces this rule to ensure that checked exceptions are properly accounted for, preventing unhandled checked exceptions from propagating unchecked.

Answer

The caller must catch only FileNotFoundException.

Answer

The caller can declare throws Exception to cover both.

Answer

The caller can ignore both exceptions.

Question 2

Which of the following correctly uses the ternary operator to set int max to the larger of two ints x and y?

Accepted Answer

int max = x > y ? x : y;. The ternary operator `? :` evaluates the boolean expression `x > y`; if true, it returns `x`, otherwise `y`, assigning the larger value to `int max`. This is the standard syntax for a conditional assignment in Java, as defined in the Java Language Specification (JLS §15.25).

Answer

int max = x > y ? y : x;

Answer

int max = if (x > y) x else y;

Answer

int max = (x > y) ? x, y;

Question 3

Refer to the exhibit. A Java source file fails to compile with the given error. What change should be made to fix the error?

Accepted Answer

Add a throws IOException clause to the enclosing method. The code is calling a method (e.g., `Files.readString()`, `BufferedReader.readLine()`, or similar) that throws a checked `IOException`. In Java, checked exceptions must be either caught with a try-catch block or declared in the enclosing method's `throws` clause. Option A adds the `throws IOException` declaration, which correctly propagates the exception to the caller, satisfying the compiler's requirement.

Answer

Wrap the code in a try-catch for NullPointerException

Answer

Change the method to use a finally block

Answer

Import the java.io.IOException class

Question 4

Which TWO are valid ways to declare and initialize an array of Strings?

Accepted Answer

String[] names = new String[]{"A", "B"};. It uses the valid syntax `new String[]{"A", "B"}` to both declare and initialize a String array in a single statement. This is the standard way to create an array with an anonymous array initializer when the declaration and initialization are combined.

Answer

String[] names = {"A", "B"}[];

Answer

String names[] = new String[2];

Answer

String[] names = {1, 2};

Question 5

What is the result of the following code? int[] arr = new int[3]; arr[3] = 5; System.out.println(arr[3]);

Accepted Answer

Runtime exception. The code attempts to access index 3 of an array of length 3. Since Java arrays are zero-indexed, valid indices are 0, 1, and 2. Accessing index 3 throws an ArrayIndexOutOfBoundsException at runtime, so option A is correct.

Answer

0

Answer

5

Answer

Compilation error

Question 6

A developer compiles a Java application using the command `javac -d bin src/com/example/App.java`. Which of the following is true?

Accepted Answer

The compiled .class files are placed in the `bin` directory maintaining the package structure.. The `-d` option in the `javac` command specifies the destination directory for compiled `.class` files. When `-d bin` is used, the compiler places the `.class` files into the `bin` directory, preserving the package directory structure (e.g., `bin/com/example/App.class`). This is the standard behavior for organizing compiled output separately from source code.

Answer

The compiler searches for source files in the `bin` directory.

Answer

The compiler creates a JAR file named `App.jar` in the `bin` directory.

Answer

The compiler compiles the code into a named module.

Question 7

You are responsible for deploying a Java desktop application that uses JavaFX and various third-party libraries. The application is modular and uses JPMS. To reduce the footprint and startup time, you decide to use jlink to create a custom runtime image that includes only the required modules. The application has a main module `com.myapp` that requires `javafx.controls`, `javafx.base`, and some other modules. After creating the runtime image using the command `jlink --module-path $JAVA_HOME/jmods:lib --add-modules com.myapp --output myapp-image`, you test the image on a development machine, and it works. However, when deploying to a customer's machine, the application fails to start with an error: "Error: Could not find or load main class com.myapp.Main". The customer's machine has no Java installed. The runtime image includes the `com.myapp` module. You verify that the `myapp-image/bin/java` launcher exists. The main class is correctly declared in the module-info.java of `com.myapp`. What is the most likely cause of this error?

Accepted Answer

Use the `--launcher` option in jlink to create a launcher script that automatically runs the main class with the correct module.. The `jlink` tool does not automatically create a launcher script that specifies the main class for the runtime image. Without the `--launcher` option, the generated `java` launcher does not know which module and main class to execute, leading to the 'Could not find or load main class' error when no Java is installed on the customer's machine. Using `--launcher` creates a custom script (e.g., `myapp`) that invokes `java --module com.myapp/com.myapp.Main`, ensuring the correct entry point is used.

Answer

Use the `--add-modules` option to include `javafx.controls` and other required modules in the command.

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Add the `--bind-services` option to jlink to automatically include service provider modules.

Answer

Ensure that the `com.myapp` module reads all required modules by adding `requires` directives in module-info.java.

Question 8

In a banking application, a class 'Account' has a private field 'balance'. Which is the best way to allow subclasses to read but not directly modify 'balance'?

Accepted Answer

Provide a public getBalance() method. It follows encapsulation: a public getBalance() method provides read-only access to the private balance field. Subclasses cannot directly modify balance because it is private. Option D (protected) is incorrect because protected access allows subclasses to directly read and write the field, which violates the requirement that subclasses should not be able to directly modify balance.

Answer

Make balance public

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Use a static variable

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Make balance protected

Question 9

A programmer writes a switch statement to handle different cases. The code compiles and runs, but the output is unexpected: 'A' prints when the input is 'B'. Which is the most likely cause?

Accepted Answer

A break statement is missing after the case 'B'.. In a switch statement, when a case matches, execution continues sequentially through subsequent cases (fall-through) unless a break statement is encountered. If case 'B' lacks a break, after executing its code, the program falls through to the code for case 'A' (or the next case), printing 'A' even though the input was 'B'. This is the classic fall-through behavior in Java.

Answer

The switch variable type is char but should be String.

Answer

The switch statement is missing a default case.

Answer

The default case is executed instead of the matched case.

Question 10

Which two of the following are valid ways to declare and initialize an array of integers? (Select two.)

Accepted Answer

int[] arr = new int[5];. It declares an integer array with a size of 5 using valid syntax, and the array is initialized with default values (0 for each element). In Java, `new int[5]` allocates memory for 5 integers and sets them to 0, which is a valid initialization.

Answer

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

Answer

int[5] arr;

Answer

int arr = new int[5];