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).finalapplies to variables, methods, and classes.finallyblock ensures resource cleanup.
🎯 Use Cases
- ✅ Use
finalfor constants and immutable references. - ✅ Use
finallyto 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.
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