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48 lines (39 loc) · 1.61 KB
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package Java8.Optional;
import Java8.StreamsApi.User;
import java.util.Optional;
public class OptionalExample {
public static void main(String[] args) {
//Optional Example
//Create an empty Optional object
Optional<String> empty = Optional.empty();
System.out.println(empty);//Optional.empty
//using is present and is empty
if (empty.isPresent()) {
System.out.println(empty.get());
} else {
System.out.println("empty is empty");//empty is empty
}
//Create a non-empty Optional object
Optional<String> nonEmpty = Optional.of("Hello");
System.out.println(nonEmpty);//Optional[Hello]
/*
//Create a non-empty Optional object with null value
Optional<String> nonEmptyWithNull = Optional.of(null);//NullPointerException
System.out.println(nonEmptyWithNull);//Null Pointer exception
*/
//optional example with user object
//Create an empty Optional object
Optional<User> emptyUser = Optional.empty();
System.out.println(emptyUser);//Optional.empty
//Create a non-empty Optional object
Optional<User> nonEmptyUser = Optional.of(new User(25, "Alex"));
System.out.println(nonEmptyUser);//Optional[User{id=25, name='Alex'}]
//Create a non-empty Optional object with null value
Optional<User> nonEmptyUserWithNull =
Optional.of(new User(25, null));
System.out.println(
nonEmptyUserWithNull);//Optional[User{age=25, name='null'}]
System.out.println(nonEmptyUserWithNull.get());//User{age=25, name='null'}
System.out.println(nonEmptyUserWithNull.get().getName());//null
}
}