Java 11 Cookbook

How to do it...

1. Create an Optional object using any of the methods that have been demonstrated, as follows:

Optional<Integer> prize1 = Optional.empty();System.out.println(prize1.isPresent()); //prints: falseSystem.out.println(prize1);   //prints: Optional.emptyOptional<Integer> prize2 = Optional.of(1000000);System.out.println(prize2.isPresent()); //prints: trueSystem.out.println(prize2);  //prints: Optional[1000000]//Optional<Integer> prize = Optional.of(null);                                   //NullPointerExceptionOptional<Integer> prize3 = Optional.ofNullable(null);System.out.println(prize3.isPresent());  //prints: falseSystem.out.println(prize3);     //prints: Optional.empty

Notice that a null value can be wrapped inside an Optional object by using the ofNullable() method. ...