Java Close Resources
When working with files, streams, or other resources, it is important to close them after use. If you forget to close a resource, it may keep using memory or even prevent you from opening the file again until the program ends.
Note
You have not yet learned about files and streams in detail. These topics will come in the next chapters. For now, just focus on how try-with-resources works.
In older code, you had to close "resources" manually by calling their close() method:
Example
import java.io.FileOutputStream;
import java.io.IOException;
public class Main {
public static void main(String[] args) {
try {
FileOutputStream output = new FileOutputStream("filename.txt");
output.write("Hello".getBytes());
output.close(); // must close manually
System.out.println("Successfully wrote to the file.");
} catch (IOException e) {
System.out.println("Error writing file.");
}
}
}Java try-with-resources
Since Java 7, you can use try-with-resources . It is a special form of try that works with resources (like files and streams ). The resource is declared inside parentheses try(...) , and Java will close it automatically when the block finishes - even if an error occurs.
Example (try-with-resources)
import java.io.FileOutputStream;
import java.io.IOException;
public class Main {
public static void main(String[] args) {
// resource is opened inside try() try (FileOutputStream output = new FileOutputStream("filename.txt")) { output.write("Hello".getBytes()); // no need to call close() here System.out.println("Successfully wrote to the file.");
} catch (IOException e) {
System.out.println("Error writing file.");
}
}
}Why use try-with-resources?
- Safer - resources are always closed, even if an exception occurs.
- Cleaner - no need to write close() calls.
- Shorter code - less boilerplate, easier to read.
Rule of thumb: Whenever you work with files, streams, or database connections, use try-with-resources to make sure they are closed properly.