Explain the difference between final, finally, and finalize in Java

💡 Concept: final, finally, and finalize

The keywords and constructs final, finally, and finalize serve very different purposes in Java despite their similar names.

📘 Quick Intro

final is a keyword used to declare constants and prevent method overriding or inheritance; finally is a block used to execute code after try-catch; finalize is a method called by the garbage collector before object destruction.

🧠 Analogy

Think of final as a locked door that cannot be changed, finally as a cleanup crew that always finishes its work, and finalize as the farewell message before demolition.

🔧 Technical Explanation

final: Prevents variable reassignment, method overriding, or inheritance.
finally: Executes code after try-catch regardless of exceptions.
finalize(): Called by GC before reclaiming object memory (deprecated in recent Java).
final applies to variables, methods, and classes.
finally block ensures resource cleanup.

🎯 Use Cases

✅ Use final for constants and immutable references.
✅ Use finally to close resources like files and streams.
✅ Avoid relying on finalize(); use try-with-resources and explicit cleanup.

💻 Java Code Example


public class Example {
    final int MAX_VALUE = 100; // constant

    void method() {
        try {
            System.out.println("Inside try");
        } catch (Exception e) {
            System.out.println("Inside catch");
        } finally {
            System.out.println("Inside finally");
        }
    }

    @Override
    protected void finalize() throws Throwable {
        System.out.println("Finalize called before GC");
    }
}

❓ Interview Q&A

Q1: What does final keyword do?
A: Prevents reassignment or inheritance.

Q2: When is finally block executed?
A: Always after try-catch.

Q3: What is finalize method?
A: Called by GC before object destruction.

Q4: Can final variables be changed?
A: No.

Q5: Is finally mandatory?
A: No, but good for cleanup.

Q6: Can you override finalize?
A: Yes, but it's deprecated.

Q7: Does finally block execute on System.exit()?
A: No.

Q8: Can final methods be overridden?
A: No.

Q9: Difference between final and finally?
A: final is keyword, finally is block.

Q10: Should you rely on finalize?
A: No, use explicit resource management.

📝 MCQs

Q1. What does final keyword do?

Allows reassignment
Prevents reassignment or inheritance
Overrides methods
None

Q2. When is finally block executed?

Only on exceptions
Only on no exceptions
Always after try-catch
Never

Q3. What is finalize method?

User method
Called by GC before object destruction
Static method
Constructor

Q4. Can final variables be changed?

Yes
No
Sometimes
Only in loops

Q5. Is finally mandatory?

Yes
No
Sometimes
Depends

Q6. Can you override finalize?

No
Yes, but deprecated
Always
Never

Q7. Does finally block execute on System.exit()?

Yes
No
Sometimes
Always

Q8. Can final methods be overridden?

Yes
No
Sometimes
Depends

Q9. Difference between final and finally?

Same
final is keyword, finally is block
Both blocks
None

Q10. Should you rely on finalize?

Yes
No, use explicit resource management
Maybe
Only for debugging

💡 Bonus Insight

Understanding these three concepts avoids confusion and improves resource management and code safety in Java.

📄 PDF Download

Need a handy summary for your notes? Download this topic as a PDF!

📄 PDF Download Coming Soon