Quick Answer
The answer is Map.of("a",1,"b",2). This is correct because the Map.of() factory method, introduced in Java 9, creates an immutable map containing exactly the key-value pairs provided as arguments, with no ability to add, remove, or modify entries after creation. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this question tests your understanding of the static factory methods in the Map interface, which are a common topic in the Collections framework section. A frequent trap is confusing Map.of() with Map.ofEntries() or assuming that Map.of() accepts a variable number of key-value pairs in a different order—remember that Map.of() takes alternating keys and values as separate arguments, not Entry objects. For quick recall, think "of" as "only fixed": Map.of() creates a fixed-size, unmodifiable map with the exact pairs you provide.
This 1Z0-829 practice question tests your understanding of working with arrays and collections. 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.
Which of the following creates an immutable map with two entries?
new HashMap<>(Map.of("a",1,"b",2))
Why wrong: Incorrect: this creates a mutable copy of the immutable map.
Map.of("a",1,"b",2)
Correct: returns an immutable map with two entries.
Collections.emptyMap()
Why wrong: Incorrect: this returns an empty immutable map.
None of the above
Why wrong: Incorrect: Map.of works.
new HashMap<>()
Why wrong: Incorrect: this creates an empty mutable map.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Map.of("a",1,"b",2)
Option B is correct because `Map.of()` returns an immutable map containing exactly the key-value pairs provided as arguments. This factory method was introduced in Java 9 and creates a fixed-size, unmodifiable map with the two entries "a"→1 and "b"→2.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
new HashMap<>(Map.of("a",1,"b",2))
Why it's wrong here
Incorrect: this creates a mutable copy of the immutable map.
Map.of("a",1,"b",2)
Why this is correct
Correct: returns an immutable map with two entries.
Related concept
Read the scenario before looking for a memorised answer.
Collections.emptyMap()
Why it's wrong here
Incorrect: this returns an empty immutable map.
None of the above
Why it's wrong here
Incorrect: Map.of works.
new HashMap<>()
Why it's wrong here
Incorrect: this creates an empty mutable map.
Common exam traps
The trap here is that candidates often confuse creating a mutable copy of an immutable map (option A) with the immutable map itself, or they overlook that `Map.of()` directly produces an immutable map without needing a wrapper.
Detailed technical explanation
Under the hood, `Map.of()` returns an instance of a package-private, static nested class (e.g., `MapN`) that stores keys and values in parallel arrays and throws `UnsupportedOperationException` on any mutating call. This immutability is enforced at runtime, not just at compile time, and the map does not accept null keys or values. In real-world scenarios, immutable maps are preferred for configuration constants or as unmodifiable return values to prevent accidental modification.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
Working with Arrays and Collections — This question tests Working with Arrays and Collections — Read the scenario before looking for a memorised answer..
The correct answer is: Map.of("a",1,"b",2) — Option B is correct because `Map.of()` returns an immutable map containing exactly the key-value pairs provided as arguments. This factory method was introduced in Java 9 and creates a fixed-size, unmodifiable map with the two entries "a"→1 and "b"→2.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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