Java OCA OCP Practice Question 2154

Question

What is the result of compiling and running the following application?. 

package names; // ww w  . j a va2s.c om

import java.util.*; 
import java.util.function.*; 

interface ApplyFilter { 
   void filter(List<String> input); 
} 
public class Main { 
   
   static Function<String,String> first = s ->  
      {System.out.println(s); return s;}; 
   
   static Predicate second = t -> "bob".equalsIgnoreCase(t); 
   
   public void process(ApplyFilter a, List<String> list) { 
      a.filter(list); 
   } 
   public static void main(String[] contestants) { 
      final List<String> people = new ArrayList<>(); 
      people.add("Bob"); 
      people.add("bob"); 
      people.add("B"); 
      people.add("A"); 
      final Main f = new Main(); 
      f.process(q -> { 
         q.removeIf(second); 
         q.forEach(first); 
      }, people); 
   } 
}
  • A. It prints two lines.
  • B. It prints three lines.
  • C. One line of code does not compile.
  • D. Two lines of code do not compile.
  • E. Three lines of code do not compile.
  • F. The code compiles but prints an exception at runtime.


D.

Note

The code does not compile, so Options A, B, and F are incorrect.

The first compilation error is in the declaration of the lambda expression for second.

It does not use a generic type, which means t is of type Object.

Since Object, unlike String, does not have a method equalsIgnoreCase(), the lambda expression does not compile.

The second compilation issue is in the lambda expression in the main() method.

Notice that process() takes an ApplyFilter instance, and ApplyFilter is a functional interface that takes a List<String> object.

q in this lambda expression is treated as an instance of List<String>.

The forEach() method defined in Collections requires a Consumer instance, not a Function, so the call q.forEach(first) does not compile.

For these two reasons, Option D is the correct answer, since the rest of the code compiles without issue.




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