Java Programs›Exceptions›Try-With-Resources

Try-With-Resources in Java

intermediate· Exceptions · Error Handling

Problem

Try-with-resources automatically calls close() on any resource that implements AutoCloseable once the try block finishes, whether it completes normally or throws — no explicit finally block needed.

Open a custom resource inside a try-with-resources statement and confirm it's closed automatically once the block finishes.

Input

try (Resource r = new Resource()) { r.use(); }

Output

Resource opened
Using resource
Resource closed

Java Program

Java

class Resource implements AutoCloseable {
    Resource() {
        System.out.println("Resource opened");
    }

    public void use() {
        System.out.println("Using resource");
    }

    @Override
    public void close() {
        System.out.println("Resource closed");
    }
}

public class TryWithResources {
    public static void main(String[] args) {
        try (Resource r = new Resource()) {
            r.use();
        }
        // close() already ran automatically before this line, with no explicit finally block
    }
}

▶ Run Code

Output

Resource opened
Using resource
Resource closed

Core Logic

Declaring the resource directly in the try statement's parentheses hands its cleanup over to the compiler, which guarantees close() runs once the block ends.

How It Works

1class Resource implements AutoCloseable declares a type the try-with-resources syntax knows how to clean up automatically.
2Its constructor prints "Resource opened", and its close() method prints "Resource closed".
3try (Resource r = new Resource()) { ... } creates the resource inside the try statement's own parentheses, rather than before the try block.
4Once the block inside the braces finishes — here, printing "Using resource" — the compiler automatically calls r.close(), with no explicit finally block written.

Running the program prints "Resource opened", then "Using resource" from inside the block, then "Resource closed" automatically once the block ends.

💡

Key Point: close() runs automatically even if the block throws an exception partway through — the same guarantee a finally block provides, but without having to write one.

Key Concepts

AutoCloseabletry-with-resourcesautomatic cleanup

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Unchecked Exception

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