OCPJP Simulation Test 105

105

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Question: What is the result of the following program?

  1 import java.util.function.*;

  2 import java.util.*;

  3 public class Test {

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

  5     Consumer<String> c1 = System.out::print;

  6     c1.accepts("printme");

  7     Supplier<Queue<String>> s2 = LinkedList::new;

  8     Queue<String> queue = s2.gets();

  9     Consumer<String> c = queue::offer;

 10     c.accepts("first entry");

 11     System.out.print(queue);}}

Choice:
A. []
B. print nothing
C. printmefirst entrynull
D. printme[first entry]
E. [first entry]
F. first entry
G. compile error
H. runtime exception



Next Question

Answer: G

Explain: Consumer functional interface takes a parameter with specified type and returns nothing. Supplier takes no parameter and returns an object of the specified type. Line 5 declared a Consumer takes String as parameter, the right side referenced System.out.print(String s) method. Line 7 declared a Supplier returns a new LinkedList<String> which implements Queue interface. Consumer's interface function is accept(), Supplier's interface function is get(). Once Consumer's accept() is called, the parameter is passed in and the corresponding method reference or lambda is called. Once Supplier's get() is called, an Object with the specified type is returned.

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