OOP-Exception try resrource

What is try-with-resources in Java?

A try statement that automatically closes resources after use

When was try-with-resources introduced?

Java 7

What is a resource in try-with-resources?

An object that must be closed after use (e.g., files, streams, DB connections)

What interface must a resource implement?

AutoCloseable

Example of AutoCloseable classes

FileInputStream, BufferedReader, Scanner, Connection

Basic syntax of try-with-resources

try(Resource res = …) { code }

What happens to resources after try block?

They are automatically closed

Do we need finally block with try-with-resources?

No, it's optional because closing is automatic

What happens if exception occurs?

Resource is still closed automatically

Can we use multiple resources?

Yes, separated by semicolons

Example with multiple resources

try(r1 = …; r2 = …) { }

Order of closing resources

Closed in reverse order of declaration

Can we catch exceptions in try-with-resources?

Yes, using catch blocks

Can we use finally with try-with-resources?

Yes, but usually not needed

What problem does try-with-resources solve?

Resource leaks (forgetting to close resources)

Difference between try-finally and try-with-resources

try-finally requires manual close; try-with-resources is automatic

What happens if close() throws exception?

It becomes a suppressed exception

What is a suppressed exception?

An exception thrown during resource closing while another exception already exists

How to get suppressed exceptions?

using getSuppressed() method

Can we declare resource outside try?

Yes (since Java 9), if it is effectively final

Example Java 9 syntax

Resource r = …; try(r) { }