// streams/Optionals.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
import java.util.*;
import java.util.stream.*;
import java.util.function.*;

public class Optionals {
 static void basics(Optional<String> optString) {
 if(optString.isPresent())
 System.out.println(optString.get());
 else
 System.out.println("Nothing inside!");
 }
 static void ifPresent(Optional<String> optString) {
 optString.ifPresent(System.out::println);
 }
 static void orElse(Optional<String> optString) {
 System.out.println(optString.orElse("Nada"));
 }
 static void orElseGet(Optional<String> optString) {
 System.out.println(
 optString.orElseGet(() -> "Generated"));
 }
 static void orElseThrow(Optional<String> optString) {
 try {
 System.out.println(optString.orElseThrow(
 () -> new Exception("Supplied")));
 } catch(Exception e) {
 System.out.println("Caught " + e);
 }
 }
 static void test(String testName,
 Consumer<Optional<String>> cos) {
 System.out.println(" === " + testName + " === ");
 cos.accept(Stream.of("Epithets").findFirst());
 cos.accept(Stream.<String>empty().findFirst());
 }
 public static void main(String[] args) {
 test("basics", Optionals::basics);
 test("ifPresent", Optionals::ifPresent);
 test("orElse", Optionals::orElse);
 test("orElseGet", Optionals::orElseGet);
 test("orElseThrow", Optionals::orElseThrow);
 }
}
/* Output:
 === basics ===
Epithets
Nothing inside!
 === ifPresent ===
Epithets
 === orElse ===
Epithets
Nada
 === orElseGet ===
Epithets
Generated
 === orElseThrow ===
Epithets
Caught java.lang.Exception: Supplied
*/