Java OCA OCP Practice Question 2651

Question

What is the result of the following code? 

public interface Checker { 
  boolean check(int height, int limit); 
} 
public class Main { 
  public static void main(String[] args) { 
     check((h, l) -> h.toString(), 5);  // x1 
  } /*from ww  w .j  a  v a  2s.co m*/
  private static void check(Checker check, int height) { 
     if (check.check(height, 10))  // x2 
        System.out.println("too high"); 
     else System.out.println("ok"); 
  } 
}
  • A. ok
  • B. too high
  • C. Compiler error on line x1.
  • D. Compiler error on line x2.
  • E. Compiler error on a different line.
  • F. A runtime exception is thrown.


C.

Note

The functional interface takes two int parameters.

The code on line x1 attempts to use them as if one is an Object, resulting in a compiler error making C the correct answer.

It also tries to return String even though the data type for the functional interface method is boolean.

It is tricky to use types in a lambda when they are implicitly specified.

Remember to check the interface for the real type.




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