Given the code fragment: `` Stream<List<String>> strs = Stream.of( Arrays.asList("text1", "text2"), Arrays.asList("text2", "text3")); Stream<String> bs2 = strs .filter(b -> b.contains("text1"))…

Question

Stream<List<String>> strs = Stream.of(
 Arrays.asList("text1", "text2"),
 Arrays.asList("text2", "text3"));
Stream<String> bs2 = strs
 .filter(b -> b.contains("text1"))
 .flatMap(rs -> rs.stream())
 .peek(b -> System.out.print(b));
bs2.forEach(b -> System.out.print(b));

Options

• Atext1text2
• Btext1text2text2text3
• Ctext1
• D[text1, text2]

• A
  73% (32)
• B
  16% (7)
• C
  5% (2)
• D
  7% (3)

Explanation

Option A is correct because filter operates on each List<String> object - b.contains("text1") returns true only for ["text1", "text2"], so the second list ["text2", "text3"] is eliminated entirely. flatMap then unwraps the surviving list into individual elements "text1" and "text2", which both flow through the pipeline and are printed via peek and forEach. Note: strictly speaking, both peek and forEach each call System.out.print, so the actual JVM output would be text1text1text2text2 - if your exam version expects text1text2, it likely intended only one print statement; understanding the pipeline logic still gets you to the right distractor eliminations.

Why the distractors are wrong:

• B (text1text2text2text3) incorrectly includes "text2" and "text3" from the second list - that entire list is removed by filter.
• C (text1) confuses what flatMap does: it flattens the whole surviving list ["text1", "text2"] into individual strings, not just the "text1" element.
• D ([text1, text2]) would only appear if you printed the list object directly, before flatMap unwrapped it into individual strings.

Memory tip: Think of it in two stages - filter decides which containers survive, then flatMap opens them and spills their contents. Here: filter keeps the box labeled "text1", flatMap empties the box one item at a time.

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