In which case will the finally block not perform its task in a try-catch-finally construct?

The finally block in a try-catch-finally construct is intended to execute code that must run regardless of whether an exception was thrown or not.

However, there are situations where finally may not execute:

• If the try or catch block calls System.exit() (in Java), which terminates the JVM.
• If a fatal error occurs, such as a virtual machine error (OutOfMemoryError, StackOverflowError), leading to an abrupt termination.
• If the thread executing finally was interrupted or stopped (for example, using the deprecated Thread.stop() method).

Example:

try {
    System.exit(0); // JVM will terminate, finally will not execute
} finally {
    System.out.println("This code may not execute");
}

Under normal conditions, finally always executes.