What is try-with-resources in Java?

It is a try block that automatically closes resources that implement AutoCloseable or Closeable, simplifying resource management.

Explain try-with-resources statement | FullStackPrep.Dev

💡 Concept: Try-With-Resources

Try-with-resources is a Java statement that ensures automatic closing of resources like streams and readers, preventing memory leaks and boilerplate code.

📘 Quick Intro

Introduced in Java 7, try-with-resources eliminates the need for finally blocks by auto-closing resources that implement the AutoCloseable or Closeable interface.

🧠 Analogy

Think of try-with-resources like a smart dishwasher. You load it once (open the resource), and after it’s done (block completes), it automatically cleans and shuts off (closes the resource). No manual cleanup needed!

🔧 Technical Explanation

Resources declared in the try block must implement AutoCloseable.
Once the try block finishes, each resource is automatically closed in reverse order of creation.
If an exception is thrown, all opened resources are still closed properly.
It simplifies code and prevents common memory/resource leaks.
Multiple resources can be declared separated by semicolons.

🎯 Use Cases

✅ Reading/writing files using BufferedReader or FileInputStream
✅ Handling JDBC database connections
✅ Network streams or any AutoCloseable resources

💻 Example: Try-With-Resources


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

public class FileExample {
    public static void main(String[] args) {
        try (BufferedReader br = new BufferedReader(new FileReader("sample.txt"))) {
            String line;
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

❓ Interview Q&A

Q1: What is try-with-resources?
A: A try block that automatically closes resources implementing AutoCloseable.

Q2: When was try-with-resources introduced?
A: Java 7.

Q3: What interface must resources implement?
A: AutoCloseable or Closeable.

Q4: Can multiple resources be declared?
A: Yes, separated by semicolons.

Q5: Does try-with-resources prevent memory leaks?
A: Yes, by ensuring proper closure.

Q6: What happens on exception in the try block?
A: All declared resources are still closed.

Q7: What is the order of closing resources?
A: Reverse order of declaration.

Q8: Can we use catch or finally with try-with-resources?
A: Yes, they are optional.

Q9: Is try-with-resources mandatory for AutoCloseable?
A: No, but it's recommended.

Q10: Is it better than try-finally?
A: Yes, it’s more concise and safer.

📝 MCQs

Q1. What is the purpose of try-with-resources?

Manually manage memory
Auto-close resources
Create exceptions
Throw errors

Q2. Which Java version introduced try-with-resources?

Java 6
Java 7
Java 8
Java 5

Q3. Which interface must be implemented?

Serializable
Cloneable
Runnable
AutoCloseable

Q4. Can try-with-resources handle multiple resources?

No
Yes
Only in Java 11
Only with JDBC

Q5. Does try-with-resources replace finally block?

No
Yes, for resource closure
Only in loops
Not applicable

Q6. Are catch/finally blocks mandatory?

Yes
No
Only catch
Only finally

Q7. Order of resource closing?

Same as declared
Alphabetical
Reverse of declaration
Random

Q8. Is AutoCloseable the same as Closeable?

Yes
No
They are unrelated
Closeable extends AutoCloseable

Q9. Does try-with-resources reduce boilerplate?

No
Yes
Sometimes
Depends

Q10. What happens if exception occurs?

Resources leak
Only some closed
Resources are still closed
Program crashes

💡 Bonus Insight

You can use try-with-resources with custom classes as long as they implement AutoCloseable. It’s not just for file and stream I/O!

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Explain try-with-resources statement