OCPJP Simulation Test 101

101

<Back to OCPJP

Question List

Question: What is the output of the following code?

  1 import java.util.function.*;

  2 public class Printing {

  3   public static void main(String...args) {

  4     Supplier<String> s1 = String::new;

  5     System.out.print(s1.get());

  6     Supplier<int> s2 = Integer::new;

  7     System.out.print(s2.get());}}

Choice:
A. no output
B. empty space followed by 0
C. 0
D. null0
E. nullnull
F. s1s2
G. code does not compile
H. code compiles but throw runtime exceptions.



Next Question

Answer: G

Explain: Supplier functional interface takes no parameter, returns an object of the defined type. Line 4 declared a Supplier returns an object of type String. String::new is the function reference. Line 6 tries to defined a Supplier returns an object of type Integer. However, the error message is:

Printing.java:6: error: unexpected type

    Supplier<int> s2 = Integer::new;

             ^

  required: reference

  found:    int
Supplier functional interface defined the method get(), which is used to get the object supplied by the supplier.

Study:  Use  the built-in interfaces included in the java.util.function package such as Predicate, Consumer, Function, and Supplier   

Create and use ArrayList, TreeSet, TreeMap, and ArrayDeque objects

Use method references with Streams