How to Use Try With Resources in Java: Simple Guide

In Java, use try-with-resources to automatically close resources like files or streams after use. Declare the resource inside the try parentheses, and Java will close it for you, avoiding manual cleanup and errors.

Syntax

The try-with-resources statement declares one or more resources inside parentheses after the try keyword. Each resource must implement AutoCloseable. Java automatically closes these resources at the end of the try block, even if exceptions occur.

• try (ResourceType resource = new ResourceType()): Declares the resource.
• ResourceType: Any class implementing AutoCloseable or Closeable.
• Automatic closing: Java calls close() on the resource when done.

java

try (ResourceType resource = new ResourceType()) {
    // use resource
} catch (Exception e) {
    // handle exceptions
}

Example

This example shows how to read the first line from a file using try-with-resources. The BufferedReader is automatically closed after reading, so you don't need to call close() manually.

java

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class TryWithResourcesExample {
    public static void main(String[] args) {
        String filePath = "example.txt";
        try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
            String firstLine = reader.readLine();
            System.out.println("First line: " + firstLine);
        } catch (IOException e) {
            System.out.println("Error reading file: " + e.getMessage());
        }
    }
}

Output

First line: Hello, world!

Common Pitfalls

Common mistakes when using try-with-resources include:

• Declaring resources outside the try parentheses, which disables automatic closing.
• Using resources that do not implement AutoCloseable or Closeable.
• Trying to reuse a resource after it is closed.

Always declare resources inside the try parentheses to ensure they close automatically.

java

/* Wrong way: resource declared outside try, no automatic closing */
BufferedReader reader = new BufferedReader(new FileReader("file.txt"));
try {
    String line = reader.readLine();
    System.out.println(line);
} finally {
    reader.close(); // manual close needed
}

/* Right way: resource declared inside try, auto-closed */
try (BufferedReader reader = new BufferedReader(new FileReader("file.txt"))) {
    String line = reader.readLine();
    System.out.println(line);
}

Quick Reference

Try-with-resources Cheat Sheet:

Feature	Description
Resource declaration	Inside parentheses after try keyword
Resource type	Must implement AutoCloseable or Closeable
Automatic closing	Java calls close() automatically at block end
Multiple resources	Separate by semicolons inside parentheses
Exception handling	Works with catch and finally blocks

Key Takeaways

Declare resources inside try parentheses to enable automatic closing.

Resources must implement AutoCloseable or Closeable interface.

Java automatically calls close() on resources even if exceptions occur.

Avoid manual resource closing to prevent leaks and errors.

You can declare multiple resources separated by semicolons in one try statement.