Java OCA OCP Practice Question 1527

Question

What is the output of the following application? 

package mypkg; //ww  w  .  ja  v  a  2  s . c om
  
interface Printable { 
   void print(double psi); 
} 
interface Displayable extends Printable { 
   void display(double tensileStrength); 
} 
public class Rectangle { 
   public static final void apply(Displayable instruction, double input) { // r1 
      instruction.display(input); 
   } 
   public static void main(String... future) { 
      final Rectangle r = new Rectangle(); 
      r.apply(x -> System.out.print(x+" bent!"), 5); 
   } 
}
  • A. 5.0 bent!
  • B. The code does not compile because Displayable is not a functional interface.
  • C. The code does not compile because of line r1.
  • D. None of the above.


B.

Note

A functional interface must contain exactly one abstract method.

The Displayable interface contains two abstract methods, print() and display(), since it extends Printable and inherits print().

The Displayable method is not a valid functional interface and therefore cannot be used as a lambda expression.

Option B is the correct answer.

The rest of the code compiles without issue.

The usage of an instance variable to call a static method, r.

apply() in the main() method, is permitted but discouraged.




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