Analysis of Java SE 8 Programmer II Exam: Question

D.

The code fragment creates a Stream of Lists of Strings, and then uses the flatMapToInt method to flatten the Stream of Lists into a Stream of Strings. Finally, it prints the result to the console.

Let's analyze the code step by step:

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Stream<List<String>> iStr = Stream.of(Arrays.asList("1", "John"), Arrays.asList("2", null)); 

This line creates a Stream of Lists of Strings. The Stream contains two Lists: ["1", "John"] and ["2", null].

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Stream<String> nInSt = iStr.flatMapToInt((x) -> x.stream()); 

This line uses the flatMapToInt method to flatten the Stream of Lists into a Stream of Strings. The flatMapToInt method applies the given function to each element of the Stream, and then concatenates the resulting Streams into a single Stream. In this case, the function x -> x.stream() is applied to each List element of the Stream, which returns a Stream of Strings for each List. The resulting Stream is then flattened into a single Stream of Strings.

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nInSt.forEach(System.out::print); 

This line prints each element of the Stream to the console, using a method reference to System.out::print.

Therefore, the output of the code fragment is:

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1John2null 

The answer is A.