Serialization in Java is one of the most vital topics. And it becomes even more important if you are planning for a Java programming interview. In the Java world, programmers commonly use Serialization during project assignments. The interviewers are keen to know whether you know about Serialization in-depth or not, whether you can handle the Serialization process or not, and a lot more. In this Java quiz, we’ll cover all the top serialization interview questions that can be asked during Java interviews and will provide you with an explanatory answer.
Any Java interview could have a minimum of 2-3 questions on this topic. If a candidate is not aware of Serialization in Java, he/she will certainly feel uncomfortable due to lack of knowledge. This post enlists the best 20 Java Serialization interview questions that are worth attempting before you plan to go for an interview. It will not only teach you about the key Java serialization concept but will keep you engaged throughout the Java quiz.
Java Serialization Interview Questions
Answer Key with Reasoning
Here’s the reasoning table briefly explaining each correct answer:
| Q# | Correct Answer | Explanation |
|---|---|---|
| 1 | Serializable, Externalizable | Serializable is a marker interface, while Externalizable allows custom serialization. |
| 2 | Serializable is a marker interface, Externalizable provides readExternal/writeExternal | Serializable uses Java’s default mechanism, Externalizable allows full control. |
| 3 | For small objects needing full serialization | Serializable is suitable for small objects where complete serialization is needed. |
| 4 | For large objects with selective fields | Externalizable helps optimize serialization by controlling which fields get serialized. |
| 5 | Not converted to byte stream | transient variables are not serialized, so they don’t become part of the byte stream. |
| 6 | Reset to default value | Transient variables are reset to default values (0 for int, null for objects) after deserialization. |
| 7 | None, it’s a marker interface | Serializable is a marker interface, meaning it has no methods to implement. |
| 8 | NotSerializableException | If an object has a non-serializable reference, NotSerializableException is thrown. |
| 9 | Not part of serialized object | static variables belong to the class, not instances, so they aren’t serialized. |
| 10 | Uses original constructor values | If a superclass is not serializable, its constructor initializes fields during deserialization. |
| 11 | Handles serialization/deserialization | writeObject() and readObject() provide custom serialization logic. |
| 12 | Externalizable with read/writeExternal, Use ObjectOutputStream/DataOutputStream, JSON data transfer | Alternative serialization techniques include Externalizable, JSON, and ObjectOutputStream. |
| 13 | Throws InvalidClassException | Changing a class structure without serialVersionUID causes InvalidClassException during deserialization. |
| 14 | Calculating hash of class | serialVersionUID should not be calculated dynamically because it can change unexpectedly. |
| 15 | Static variables allocated once | static variables aren’t serialized because they are class-level properties. |
| 16 | int=0, Integer=null | int resets to 0, and Integer becomes null after deserialization. |
| 17 | Use writeObject/readObject throwing NotSerializableException | Overriding writeObject()/readObject() and throwing NotSerializableException prevents serialization. |
| 18 | When superclass is added to a serializable class | readObjectNoData() ensures backward compatibility when a superclass is added. |
| 19 | NotSerializableException | If a field is not serializable, NotSerializableException is thrown. |
| 20 | Prevents direct access to object | Serialization Proxy Pattern uses a separate proxy object to improve security and prevent direct access. |
Key Takeaways from Java Serialization Quiz
Hopefully, these Java Serialization Interview Questions will have helped you learn and gain confidence in your overall Java skills. We sincerely wish you success and thank you for attempting this Java quiz. We recommend that don’t stop after the quiz instead check out some other wonderful quizzes and tutorials on Java/Python/Selenium and related programming stuff on our blog.
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