1Z0-811 Exception Handling and Development Tools — Timed 20 Questions

Question 1

A developer writes a method that reads a file and processes its contents. If the file does not exist, the method should notify the caller. Which exception should the method declare in its throws clause?

Accepted Answer

FileNotFoundException. Option B is correct because `FileNotFoundException` is a checked exception that specifically indicates a file cannot be found at the specified path. The method must declare it in its `throws` clause to notify the caller that this condition can occur and must be handled or re-declared, as required by Java's checked exception rules.

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RuntimeException

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Exception

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IOException

Question 2

A team is developing a Java application that uses many third-party libraries. One library throws a checked exception that is not declared in its method signature. Which approach best handles this situation?

Accepted Answer

Wrap the exception in a RuntimeException and throw it.. Option C is correct because a checked exception that is not declared in a method signature cannot be propagated without handling it. Wrapping it in a RuntimeException (an unchecked exception) bypasses the compiler's checked-exception enforcement, allowing the exception to be thrown without modifying the method signature. This is a common pattern when integrating third-party libraries that throw checked exceptions from methods that do not declare them.

Answer

Ignore the exception because it is not declared.

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Declare the library's exception in the method signature.

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Catch the exception and log it, then continue execution.

Question 3

Which of the following is the best practice for resource management in Java?

Accepted Answer

Use try-with-resources statement.. Option C is correct because the try-with-resources statement (introduced in Java 7) automatically closes each resource declared in its header when the block exits, whether normally or due to an exception. This eliminates the need for explicit cleanup code and ensures that resources implementing `AutoCloseable` are closed reliably, preventing resource leaks.

Answer

Close resources in a finally block without null checks.

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Rely on garbage collection to close resources.

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Use a try-catch block and close resources in the catch block.

Question 4

A developer encounters an ArrayIndexOutOfBoundsException while running a unit test. The stack trace shows the error occurs in a method that is called from many places. Which tool or technique would most efficiently identify the specific call path?

Accepted Answer

Set a breakpoint in the method and debug the test.. Setting a breakpoint in the method and debugging the test allows the developer to inspect the call stack at runtime, immediately revealing the exact sequence of method invocations that led to the ArrayIndexOutOfBoundsException. This is the most efficient approach because it directly captures the specific call path without requiring manual tracing or post-hoc analysis.

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Review the code manually to trace all possible callers.

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Run a static analysis tool to detect the issue.

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Add log statements at the beginning of the method.

Question 5

Which statement about the Java compiler is true?

Accepted Answer

It translates Java source code into bytecode.. The Java compiler (javac) translates human-readable Java source code (.java files) into platform-independent bytecode (.class files). This bytecode is then executed by the Java Virtual Machine (JVM), not directly by the operating system. Option D correctly identifies this translation step.

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It translates Java source code into native machine code.

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It produces executable files that run directly on the OS.

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It executes Java programs.

Question 6

A method throws a checked exception. Which of the following is the correct way to handle it in the calling method?

Accepted Answer

Enclose the call in a try-catch block.. Option C is correct because checked exceptions must be handled by the calling method either by catching them with a try-catch block or by declaring them in a throws clause. Since the question asks for the correct way to handle it, enclosing the call in a try-catch block is a valid and direct handling approach that prevents the exception from propagating unhandled.

Answer

Ignore the exception since it is checked.

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Add a throws clause to the calling method.

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Use a finally block without catch.

Question 7

Which command is used to run a Java application from the command line?

Accepted Answer

java. The `java` command is the correct tool to launch a Java application from the command line. It invokes the Java Virtual Machine (JVM) to load and execute the compiled bytecode contained in `.class` files or a JAR file. Without this command, the application cannot run.

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jar

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javac

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javadoc

Question 8

Which TWO statements about the finally block are true? (Choose two.)

Accepted Answer

The finally block is used for resource cleanup.. Option C is correct because the finally block is specifically designed for resource cleanup, such as closing file streams or database connections, ensuring that cleanup code runs regardless of whether an exception occurs. This is a fundamental use case in Java exception handling to prevent resource leaks.

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A try block must be followed by either a catch or finally.

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The finally block executes only if an exception is thrown.

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The finally block cannot contain a return statement.

Question 9

Which THREE are checked exceptions in Java? (Choose three.)

Accepted Answer

SQLException. SQLException is a checked exception in Java because it extends Exception directly (not RuntimeException). Checked exceptions must be either caught with a try-catch block or declared in the method signature using the throws clause. SQLException is thrown when there is a database access error or other SQL-related issues, forcing the developer to handle potential failures at compile time.

Answer

ArrayIndexOutOfBoundsException

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NullPointerException

Question 10

Given the stack trace above, which line in MyClass.java caused the exception?

Accepted Answer

Line 25. The stack trace indicates that an exception occurred in MyClass.java at line 25, which is the line that calls a method that throws an unchecked exception (e.g., an ArithmeticException from division by zero or a NullPointerException). The stack trace shows the exact line number where the exception was thrown, and since the question states that line 25 is correct, that is the line in MyClass.java that caused the exception.

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Line 30

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Line 10

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Line 15

Question 11

Given the compilation error above, which fix would resolve the error?

Accepted Answer

Wrap the code in a try-catch block for FileNotFoundException.. Option C is correct because the compilation error indicates that the code uses a constructor or method that throws a checked `FileNotFoundException` (a subclass of `IOException`). In Java, checked exceptions must be either caught with a try-catch block or declared in the method signature. Wrapping the code in a try-catch block for `FileNotFoundException` handles the exception locally, resolving the compilation error without altering the method signature.

Answer

Add a throws FileNotFoundException clause to the main method.

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Change FileReader to BufferedReader.

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Use FileInputStream instead.

Question 12

You are a Java developer at a financial firm. The application processes transactions from a queue. The team recently migrated from Java 8 to Java 11. After the migration, the application intermittently throws an exception: 'java.lang.reflect.InaccessibleObjectException: Unable to make field private final byte[] java.lang.String.value accessible: module java.base does not 'opens java.lang' to unnamed module'. This error occurs when the application tries to use reflection to access private fields of String objects for serialization. The application runs on a server where you cannot modify the JVM startup scripts. However, you can modify the application code and the module-info.java file. You need to resolve the exception without breaking existing functionality. Which approach should you take?

Accepted Answer

Refactor the code to use public APIs instead of reflecting on String's internal fields.. Option A is correct because the root cause is that the application uses reflection to access private fields of java.lang.String, which is prohibited in Java 9+ by default due to module system encapsulation. Refactoring to use public APIs (e.g., String.getBytes(), String.charAt()) eliminates the need for reflection entirely, resolving the InaccessibleObjectException without requiring JVM flags or module declarations, and preserves compatibility with Java 11.

Answer

Add --add-opens java.base/java.lang=ALL-UNNAMED to the JVM command line.

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Use sun.misc.Unsafe to access the String field directly.

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Add 'opens java.lang;' to the module-info.java file.

Question 13

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

Question 14

Match each Java keyword to its use.

Question 15

A developer writes a method that reads a file and must ensure the file is closed even if an exception occurs. Which construct should be used?

Accepted Answer

A try-with-resources statement. try-with-resources automatically closes resources that implement AutoCloseable, ensuring closure even if an exception occurs. Option D is correct. Option A (try-catch-finally without close) does not guarantee closure if exception occurs before close. Option B (throws declaration) does not handle closure. Option C (finally block alone) requires explicit close, which might be missed.

Answer

A throws declaration in the method signature

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A finally block without any resource declaration

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A try-catch-finally block with explicit close in finally

Question 16

Which of the following exceptions is a checked exception?

Accepted Answer

IOException. Option C is correct because IOException is a checked exception in Java, meaning it must be either caught or declared in the method signature using a try-catch block or throws clause. Checked exceptions are subclasses of Exception (excluding RuntimeException and its subclasses), and IOException directly extends Exception, making it subject to compile-time checking.

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ArrayIndexOutOfBoundsException

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ArithmeticException

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NullPointerException

Question 17

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

Accepted Answer

The caller must handle or declare both exceptions.. Option C is correct because 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.

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The caller must catch only FileNotFoundException.

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The caller can declare throws Exception to cover both.

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The caller can ignore both exceptions.

Question 18

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.. Option C is correct because 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.

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The exception is caught and handled by the finally block.

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The finally block does not execute if an exception occurs.

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The method exits immediately without executing finally.

Question 19

Which command compiles a Java file and generates a .class file?

Accepted Answer

javac. The `javac` command is the Java compiler, which translates Java source code (`.java` files) into bytecode stored in `.class` files. This is the standard compilation step in the Java development process, as defined by the Java SE specification.

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jar

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javadoc

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java

Question 20

A custom exception class must extend which class to be a checked exception?

Accepted Answer

Exception. Option D is correct because, in Java, a checked exception is any exception that is a subclass of `Exception` but not a subclass of `RuntimeException`. To create a custom checked exception, your class must extend `Exception` (or a subclass of `Exception` that is itself a checked exception). This forces callers to handle or declare the exception, enforcing compile-time checking.

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Throwable

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Error

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RuntimeException