1Z0-829 Java I/O API and Securing Applications Practice Question
A class implements Serializable but the developer wants to completely prevent deserialization of its instances. Which approach accomplishes this?
⚠ Common exam trap
Test-takers frequently confuse readResolve() with readObject(), thinking that returning null from readResolve() prevents deserialization, when in fact readResolve() runs after the object is already created, so it does not stop the deserialization process itself.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Override readObject() to throw an InvalidClassException.
Overriding readObject() to throw an InvalidClassException (or any exception) prevents the deserialization mechanism from completing. When an ObjectInputStream calls readObject() on a class that defines its own readObject() method, that custom method is invoked instead of the default deserialization. Throwing an exception inside readObject() aborts the deserialization process, effectively blocking the reconstruction of the instance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Override readResolve() to return a null.
Why it's wrong here
readResolve() is called after deserialization; it cannot prevent the process from starting.
- ✓
Override readObject() to throw an InvalidClassException.
Why this is correct
This causes deserialization to fail immediately.
- ✗
Override writeObject() to encrypt the object.
Why it's wrong here
Encrypting during serialization doesn't prevent deserialization; the object can still be decrypted.
- ✗
Override writeReplace() to throw an exception.
Why it's wrong here
writeReplace() is invoked during serialization, not deserialization.
Go deeper
Related to this question
About these practice questions
Courseiva writes every 1Z0-829 question from scratch — 513 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 1Z0-829 practice question is part of Courseiva's free Oracle certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 1Z0-829 exam.