- A
Deserialization succeeds and the new field is set to its default value.
With matching serialVersionUID, deserialization maps fields; new fields get default values.
- B
Deserialization succeeds only if the new field is marked transient.
Why wrong: Transient fields are not serialized, but the new field will be default even if not transient.
- C
Deserialization throws StreamCorruptedException due to missing field.
Why wrong: StreamCorruptedException indicates corruption, not compatibility issues.
- D
Deserialization throws InvalidClassException because the class definition has changed.
Why wrong: InvalidClassException occurs only if serialVersionUID mismatches, which it does not here.
Question 183 of 519
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 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
✓
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 practitioner preparing for the 1Z0-829 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Questions learners often ask
What does this 1Z0-829 question test?
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.
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Last reviewed: Jun 25, 2026
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