Quick Answer
The answer is that Map.merge() associates the key with the given value when the key is absent. This behavior is defined by the method’s contract: if the specified key is not already present in the map, or if it is present but maps to null, the remapping function is never invoked, and the key is simply bound to the provided non-null value. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this tests your understanding of the merge method’s three-case logic—present, absent, or null—and is often used in questions about functional programming with maps. A common trap is assuming the remapping function runs for absent keys, but it only executes when the key already has a non-null value. For a quick memory tip: think of merge as “add if missing, combine if present”—when the key is absent, it’s just a straightforward put.
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.
What does the Map.merge() method do if the specified key is absent?
Calls the remapping function with null and the value
Why wrong: Remapping is called when key is present.
Associates the key with the given value
If absent, put value.
Throws NullPointerException
Why wrong: Only if value or remapping is null.
Removes the key if present
Why wrong: That's not merge.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Associates the key with the given value
When the specified key is absent in the map, the `Map.merge()` method associates the key with the given value without invoking the remapping function. This is specified in the Java API documentation: if the key is not present (or maps to null), the key is associated with the given non-null value.
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.
Calls the remapping function with null and the value
Why it's wrong here
Remapping is called when key is present.
Associates the key with the given value
Why this is correct
If absent, put value.
Related concept
Read the scenario before looking for a memorised answer.
Throws NullPointerException
Why it's wrong here
Only if value or remapping is null.
Removes the key if present
Why it's wrong here
That's not merge.
Common exam traps
Oracle often tests the misconception that the remapping function is always called, leading candidates to incorrectly choose option A, when in fact the function is only invoked for existing keys.
Detailed technical explanation
Under the hood, `Map.merge()` uses a `computeIfAbsent`-like pattern: if the key is absent, it directly puts the value (or the result of the remapping function if the key were present). A subtle behavior is that if the remapping function returns null when the key is present, the key is removed; but when the key is absent, no removal occurs. This method is particularly useful for concurrent maps (e.g., `ConcurrentHashMap`) where atomicity is critical for operations like word counting or merging cached results.
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.
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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: Associates the key with the given value — When the specified key is absent in the map, the `Map.merge()` method associates the key with the given value without invoking the remapping function. This is specified in the Java API documentation: if the key is not present (or maps to null), the key is associated with the given non-null value.
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 30, 2026
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