About Question enthuware.ocpjp.v8.2.1891 :

[in2xes]

4. System.out.println(names.stream().collect(Collectors.mapping(x->x, Collectors.summarizingInt(x->x))).getSum());

5. System.out.println(names.stream().collect(Collectors.summarizingInt(x->x)).getSum());

both options does not even compile. so answer is 2.

Or change 4 and 5 to

System.out.println(names.stream().collect(Collectors.summarizingInt(x->Integer.valueOf(x.toString()))).getSum());
System.out.println(names.stream().collect(Collectors.mapping(x->x, Collectors.summarizingInt(x->Integer.valueOf(x.toString())))).getSum());

[admin]

Not sure why you think it will not compile. I just compiled the code and ran it. It worked as expected:

Code: Select all

import java.util.*;
import java.util.stream.*;
public class TestClass {
  public static void main(String[] args) {
    List<Integer> names = Arrays.asList(1, 2, 3);

    System.out.println(names.stream().mapToInt(x->x).sum());

    System.out.println(names.stream().reduce(0, (a, b)->a+b));

    System.out.println(names.stream().collect(Collectors.mapping(x->x, Collectors.summarizingInt(x->x))).getSum());

    System.out.println(names.stream().collect(Collectors.summarizingInt(x->x)).getSum());

 }

}

It prints 6 four times.

[in2xes]

Sorry. One of the option is working but not other. I'm yet to figure out the root cause. See attached image for compilation failure.

[admin]

Can't comment on messages shown by an IDE. Try the command line.

[ramy6_1]

Hello ,

At Oracle exam topics section 4.6 , it mentioned averagingDouble(), groupingBy(), joining(), and partitioningBy() from Collector class.
Does that mean other functions also included at exam I.e Collectors.summarizingInt ?

[admin]

Yes, you should know about summarizingInt also. It is quite simple though.

HTH,
Paul.

[henrid]

It is ridiculous having to memorize the whole API. That is NOT simple. But okay, you guys didn't create the exam.