Explain try-with-resources statement
💡 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
BufferedReaderorFileInputStream - ✅ Handling JDBC database connections
- ✅ Network streams or any
AutoCloseableresources
💻 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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