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Working with Streams and Lambda Expressions →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is {apple=3, banana=2, orange=1}. This output results from using the `groupingBy` collector with a downstream `counting` collector on a stream of words, which groups each distinct word and counts its occurrences in the stream. The `groupingBy` classifier function maps each word to itself as the key, while `counting()` tallies the number of times each key appears, producing a `Map<String, Long>`. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this pattern tests your understanding of the `Collectors` utility class and how downstream collectors compose to transform stream data. A common trap is forgetting that `groupingBy` with `counting` returns a `Long` value, not an `Integer`, so watch for type mismatches in exam code. Another pitfall is confusing `groupingBy` with `toMap`—remember that `groupingBy` always groups by a classifier, while `toMap` requires explicit key and value mappers. Memory tip: think of `groupingBy` as sorting items into labeled buckets, then `counting` as tallying each bucket’s contents.

1Z0-829 Working with Streams and Lambda Expressions Practice Question

This 1Z0-829 practice question tests your understanding of working with streams and lambda expressions. 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.

Exhibit

List<String> items = List.of("apple", "banana", "apple", "orange", "banana", "apple");
Map<String, Long> countMap = items.stream()
    .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
System.out.println(countMap);

Refer to the exhibit. What is the output?

Question 1hardmultiple choice
Full question →

Exhibit

List<String> items = List.of("apple", "banana", "apple", "orange", "banana", "apple");
Map<String, Long> countMap = items.stream()
    .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
System.out.println(countMap);

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

✓

{apple=3, banana=2, orange=1}

The stream collects a map from each word to its count. Apple appears 3 times, banana 2, orange 1. Output: {apple=3, banana=2, orange=1}.

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.

  • ✗

    {apple=2, banana=2, orange=2}

    Why it's wrong here

    Incorrect.

  • ✗

    {1=[apple, banana, orange], 2=[apple, banana], 3=[apple]}

    Why it's wrong here

    Incorrect; that is grouping by count, not counting.

  • ✓

    {apple=3, banana=2, orange=1}

    Why this is correct

    Correct.

    Related concept

    Read the scenario before looking for a memorised answer.

  • ✗

    {apple=3, banana=1, orange=1}

    Why it's wrong here

    Incorrect; banana appears twice.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.

Detailed technical explanation

How to think about this question

This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.

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.
  • Use explanations to understand the rule behind the answer.

TExam Day Tips

  • Underline the problem statement mentally.
  • 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

Got this wrong? Here's your next step.

Identify which 1Z0-829 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.

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FAQ

Questions learners often ask

What does this 1Z0-829 question test?

Working with Streams and Lambda Expressions — This question tests Working with Streams and Lambda Expressions — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: {apple=3, banana=2, orange=1} — The stream collects a map from each word to its count. Apple appears 3 times, banana 2, orange 1. Output: {apple=3, banana=2, orange=1}.

What should I do if I get this 1Z0-829 question wrong?

Identify which 1Z0-829 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

About these practice questions

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Same concept, more angles

1 more ways this is tested on 1Z0-829

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. Given a list of strings, which of the following will produce a Map<String, Long> counting the occurrences of each string?

hard
  • A..collect(Collectors.toMap(Function.identity(), String::length))
  • ✓ B..collect(Collectors.groupingBy(Function.identity(), Collectors.counting()))
  • C..collect(Collectors.groupingBy(Function.identity(), Collectors.summingInt(e->1)))
  • D..collect(Collectors.toMap(Function.identity(), v->1))

Why B: Collectors.groupingBy with Collectors.counting() correctly counts occurrences and returns Map<String, Long>.

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Last reviewed: Jun 25, 2026

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