Question

What is the purpose of the addShutdownHook(Runnable r) method?

1) To add a hook for performing cleanup actions when the JVM is shutting down
2) To add a hook for starting a new thread when the JVM is shutting down
3) To add a hook for handling exceptions when the JVM is shutting down
4) To add a hook for modifying the JVM's shutdown behavior

Answer 1

The addShutdownHook(Runnable r) method in Java is used to add a thread that performs cleanup actions before the JVM shuts down, ensuring a graceful shutdown and resource release.

Step-by-step explanation:

The purpose of the addShutdownHook(Runnable r) method in Java is to add a hook for performing cleanup actions when the JVM (Java Virtual Machine) is shutting down. This functionality is critical for releasing resources or performing other important tasks needed before the application stops running. When the JVM initiates its shutdown sequence, which can happen because of several reasons such as a user request, or system-wide shutdown, all registered shutdown hooks are started and allowed to run concurrently to complete their work. These hooks are user-defined threads that can perform tasks like closing files, safely shutting down network connections, or releasing any other system resources.

Shutdown hooks are a way to ensure a graceful shutdown of an application. They are particularly useful in scenarios where an abrupt shutdown may lead to undesirable consequences like data corruption or loss. Therefore, selecting the correct option from the ones provided, the answer is (1) To add a hook for performing cleanup actions when the JVM is shutting down.

Answer 2

The purpose of the addShutdownHook(Runnable r) method is to add a hook for performing cleanup actions when the JVM is shutting down (Option 1).

Step-by-step explanation:

Cleanup Actions: The addShutdownHook method in Java allows developers to register a shutdown hook, which is a thread that will be executed when the JVM is shutting down. This is commonly used to perform cleanup tasks such as closing open resources, saving data, or releasing acquired locks.

Not for Starting Threads: It is not intended for starting new threads (Option 2) but rather for executing code during the JVM shutdown process.

Not for Exception Handling: It is not primarily used for handling exceptions during shutdown (Option 3). The focus is on cleanup tasks.

Not for Modifying Shutdown Behavior: While the hook allows additional cleanup, it does not modify the overall shutdown behavior of the JVM (Option 4).

Option 1 is the answer.