BUET M.Sc. Admission — Department of CSE — May: 2019প্রশ্ন ও সমাধান

try-with-resources (introduced in Java 7) automatically closes any resource (file streams, database connections, sockets) that implements the AutoCloseable interface once the try block finishes - whether it finishes normally or via an exception - without needing an explicit finally block.

Why it's used instead of a plain try/finally:

• Guarantees resource cleanup: eliminates the classic bug of a forgotten close() call, which causes resource/memory leaks (e.g., too many open file handles).
• Cleaner code: removes the boilerplate of a finally { if (x != null) x.close(); } block.
• Correct exception handling: if both the try block and the automatic close() throw exceptions, Java keeps the original exception as primary and attaches the close-exception as a suppressed exception (visible via getSuppressed()) - a plain try/finally would silently lose the original exception.

flowchart TD
A([try-with-resources block starts]) --> B[Resource opened]
B --> C[Code executes inside try]
C --> D[Block ends normally or throws exception]
D --> E[JVM automatically calls resource.close]
E --> F([Resource guaranteed closed])

Example:

try (BufferedReader br = new BufferedReader(new FileReader("data.txt"))) {
    System.out.println(br.readLine());
}   // br.close() is called automatically here, even if readLine() throws

Exam takeaway: try-with-resources replaces manual finally { close(); } boilerplate and never silently loses the original exception to a close() failure - any resource used this way must implement AutoCloseable/Closeable.