Java OCA OCP Practice Question 1741

Question

Which line can replace line 18 without changing the output of the program? 

1:   class Car {// w w  w. j a v  a2  s  .  com
2:      private int number;
3:      public Car(int n) {
4:         number = n;
5:      }
6:      public int getNumber() {
7:         return number;
8:      }
9:      public boolean isNew() {
10:        return number < 4*60;
11:     }
12:   }
13:   public class Main {
14:     public static void main(String[] args) {
15:        Stream<Car> runners = Stream.of(new Car(250),
16:           new Car(600), new Car(201));
17:        long count = runners
18:             .filter(Car::isNew)
19:             .count();
20:        System.out.println(count);
21:    }
22:  }

A.   .map(Car::isNew)

B.   .mapToBool(Car::isNew)
     .filter(b -> b == true)

C.   .mapToBoolean(Car::isNew)
     .filter(b -> b == true)

D.  None of the above



D.

Note

There is no built-in method to map a value to a boolean primitive.

Therefore, Options B and C don't even compile, so they are incorrect.

Option A does compile as it maps a Car to a Boolean.

It doesn't actually filter() the stream to eliminate any values, so the output is not the same.

It prints 3 instead of 1.

None of these are correct, making Option D the answer.




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