The correct answer is that deserialization succeeds and the new field is set to its default value. This happens because the unchanged serialVersionUID of 123L signals to the Java deserialization mechanism that the class definition is compatible with the serialized stream, even though the class now has an additional field. The Object Serialization Specification permits forward compatibility when the serialVersionUID matches, so the missing field in the old stream is simply initialized to its default value—null for objects, 0 for numeric primitives, or false for booleans—without throwing an InvalidClassException. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this tests your understanding of serialization compatibility and the role of the serialVersionUID field change; a common trap is assuming any structural change breaks deserialization. Remember the mnemonic: “Same UID, new field? Default yield.”
1Z0-829 Java I/O API and Securing Applications Practice Question
This 1Z0-829 practice question tests your understanding of java i/o api and securing applications. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A serialized object has an explicitly declared serialVersionUID of 123L. After a code change, a new field is added to the class but the serialVersionUID is left unchanged. What happens when deserializing an old stream?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deserialization succeeds and the new field is set to its default value.
Option A is correct because when a serialized object has an unchanged serialVersionUID, the Java deserialization mechanism treats the class as compatible. The new field is not present in the old stream, so it is simply initialized to its default value (e.g., null for objects, 0 for primitives) without throwing an exception. This behavior is defined by the Java Object Serialization Specification, which allows forward compatibility as long as the serialVersionUID matches.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Deserialization succeeds and the new field is set to its default value.
Why this is correct
With matching serialVersionUID, deserialization maps fields; new fields get default values.
Related concept
Read the scenario before looking for a memorised answer.
✗
Deserialization succeeds only if the new field is marked transient.
Why it's wrong here
Transient fields are not serialized, but the new field will be default even if not transient.
✗
Deserialization throws StreamCorruptedException due to missing field.
Why it's wrong here
StreamCorruptedException indicates corruption, not compatibility issues.
✗
Deserialization throws InvalidClassException because the class definition has changed.
Why it's wrong here
InvalidClassException occurs only if serialVersionUID mismatches, which it does not here.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume any class change (like adding a field) will break deserialization, but the exam tests that a matching serialVersionUID allows the new field to be silently defaulted, not that it causes an exception.
Detailed technical explanation
How to think about this question
Under the hood, Java serialization uses a class descriptor hash (the serialVersionUID) to verify class compatibility. When the UID matches, the deserialization process reads fields from the stream in order, and any fields in the local class that are not present in the stream are simply skipped and initialized to their default values. This mechanism supports forward compatibility, but it can lead to subtle bugs if the new field's default value is not semantically appropriate for the application logic.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Java I/O API and Securing Applications — This question tests Java I/O API and Securing Applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Deserialization succeeds and the new field is set to its default value. — Option A is correct because when a serialized object has an unchanged serialVersionUID, the Java deserialization mechanism treats the class as compatible. The new field is not present in the old stream, so it is simply initialized to its default value (e.g., null for objects, 0 for primitives) without throwing an exception. This behavior is defined by the Java Object Serialization Specification, which allows forward compatibility as long as the serialVersionUID matches.
What should I do if I get this 1Z0-829 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.