Chapter SEVEN
Error Handling and Exceptions

Answers

1. The correct answer is B.

Explanation:

• A. A checked exception is a type of exception that inherits from the java.lang.RuntimeException class.
  • This option is incorrect. A checked exception does not inherit from java.lang.RuntimeException. Checked exceptions are subclasses of java.lang.Exception but not of java.lang.RuntimeException.
• B. A checked exception must be either caught or declared in the method signature using the throws keyword.
  • This option is correct. Checked exceptions must be either caught using a try-catch block or declared in the method signature with the throws keyword. This is to ensure that the exception is properly handled at some point in the code.
• C. A checked exception is an error that is typically caused by the environment in which the application is running, and it cannot be handled by the application.
  • This option is incorrect. It describes errors more accurately than checked exceptions. Errors are typically caused by the environment and are not expected to be handled by the application.
• D. A checked exception can be thrown by the Java Virtual Machine when a severe error occurs, such as an out-of-memory error.
  • This option is incorrect. It describes errors rather than checked exceptions. Errors like out-of-memory errors are thrown by the JVM and are not meant to be caught or handled by applications in most cases.

2. The correct answer is A.

Explanation:

• A. This code defines a custom checked exception and correctly throws and handles it.
  • This option is correct. The code defines a custom checked exception by extending Exception. The methodThatThrowsException method throws this custom exception, which is then caught and handled in the main method.
• B. This code defines a custom unchecked exception.
  • This option is incorrect. The code extends Exception, not RuntimeException, making it a checked exception rather than an unchecked one.
• C. This code will not compile because the custom exception is not declared correctly in the method signature.
  • This option is incorrect. The custom exception is correctly declared in the method signature of methodThatThrowsException, so it will compile without issues.
• D. This code will compile but will not throw the custom exception at runtime.
  • This option is incorrect. The code will throw the custom exception at runtime as expected, and it will be caught and handled in the catch block.

3. The correct answer is B.

Explanation:

• A. 1
  • This option is incorrect. Although the catch block returns 1, the finally block will override this return value with 2.
• B. 2
  • This option is correct. The finally block always executes and its return value overrides the return value from the catch block, resulting in 2 being printed.
• C. Compilation fails
  • This option is incorrect. The code compiles without any errors.
• D. An exception occurs at runtime
  • This option is incorrect. While a RuntimeException is thrown in the try block, it is caught by the catch block, and no exception propagates to cause a runtime error.

4. The correct answer is D.

Explanation:

• A. The code doesn’t compile correctly.
  • This option is incorrect. The code does compile correctly. A try block can be followed by a finally block without a catch block.
• B. The code would compile correctly if we add a catch block.
  • This option is incorrect. While adding a catch block is valid, it is not necessary for the code to compile. The try block can be used with only a finally block.
• C. The code would compile correctly if we remove the finally block.
  • This option is incorrect. Removing the finally block is not necessary for the code to compile. The code is valid with the finally block present.
• D. The code compiles correctly as it is.
  • This option is correct. The code compiles correctly as it is. A try block must be followed by either a catch block, a finally block, or both.

5. The correct answers are C and D.

Explanation:

• A. In a try-with-resources, the catch block is required.
  • This option is incorrect. In a try-with-resources statement, the catch block is optional. The primary purpose of try-with-resources is to ensure that each resource is closed at the end of the statement, whether an exception is thrown or not.
• B. The throws keyword is used to throw an exception.
  • This option is incorrect. The throws keyword is used in method declarations to specify that the method can throw an exception, not to throw an exception. The throw keyword is used to actually throw an exception.
• C. In a try-with-resources block, if you declare more than one resource, they have to be separated by a semicolon.
  • This option is correct. In a try-with-resources block, if you declare more than one resource, they must be separated by a semicolon.
• D. If a catch block is defined for an exception that couldn’t be thrown by the code in the try block, a compile-time error is generated.
  • This option is correct. If a catch block is defined for an exception that cannot be thrown by the code in the try block, the compiler will generate an error because the catch block is unreachable.

6. The correct answer is E.

Explanation:

• A. Close Exception
  • This option is incorrect. While the IOException from close() will occur, it will be suppressed by the RuntimeException.
• B. RuntimeException
  • This option is incorrect. The primary exception is RuntimeException, but it will not print its message directly because the catch block does not handle it.
• C. RuntimeException and then CloseException
  • This option is incorrect. Although both exceptions occur, the RuntimeException is primary, and the IOException is suppressed. Both messages are not printed in sequence.
• D. Compilation fails
  • This option is incorrect. The code compiles without any errors.
• E. The stack trace of an uncaught exception is printed.
  • This option is correct. The RuntimeException thrown in the try block is not caught by the catch (IOException e) block. Hence, the stack trace of the RuntimeException is printed.

7. The correct answers are B and C.

Explanation:

• A. java.io.FileNotFoundException is incorrect. It is a subclass of java.io.IOException, which in turn is a subclass of java.lang.Exception, making it a checked exception.

• B. java.lang.ArithmeticException is correct. It is a direct subclass of java.lang.RuntimeException and represents arithmetic errors such as division by zero.

• C. java.lang.ClassCastException is correct. It is a direct subclass of java.lang.RuntimeException and indicates an invalid cast operation.

• D. java.lang.InterruptedException is incorrect. It is a direct subclass of java.lang.Exception, making it a checked exception. It indicates that a thread has been interrupted.

8. The correct answer is D.

Explanation:

• A. Only "Try Block Exception" is printed.
  • This option is incorrect. The Try Block Exception is the main exception and is not directly printed because the catch block checks for suppressed exceptions first.
• B. Only "Close Exception" is printed.
  • This option is incorrect. The Close Exception is not directly printed; it is suppressed and accessed via the getSuppressed method.
• C. Both "Try Block Exception" and "Close Exception" are printed.
  • This option is incorrect. The code only prints suppressed exceptions, not the main exception message directly.
• D. "Suppressed: Close Exception" is printed.
  • This option is correct. The RuntimeException thrown in the try block is the main exception, and the RuntimeException from the close method is suppressed. The catch block prints the suppressed exception message, "Suppressed: Close Exception".