Java Stream Filter and allMatch Example
Question
Given the code fragment: List<String> colors = Arrays.asList("red", "green", "yellow"); Predicate<String> test = n - > { System.out.println("Searching""); return n.contains("red"); }; colors.stream() .filter(c -> c.length() > 3) .allMatch(test); What is the result?
Answers
Explanations
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A. B. C. D.A.
The code creates a List of Strings called colors with three elements: "red", "green", and "yellow". It also creates a Predicate<String> called test which takes a String and returns true if the string contains the substring "red", and prints "Searching..." to the console.
The stream() method is called on the colors List, which returns a Stream of Strings. The filter() method is then called on this Stream with a lambda expression that filters out all Strings with a length less than or equal to 3.
Finally, the allMatch() method is called on the resulting Stream with the test Predicate. This method returns true if all elements of the Stream match the given Predicate.
Since the only element in the filtered Stream is "green" which does not contain the substring "red", the test Predicate will return false for this element. Therefore, the allMatch() method will return false.
However, before the test Predicate is applied, it is printed "Searching..." to the console once for each element in the Stream. Therefore, the output of the code will be:
Searching... Searching...
So the correct answer is B.
