Create Optional Object

Description

The Optional<T> class provides three static factory methods to create Optional objects.

• <T> Optional<T> empty()
  Returns an empty Optional.
  The Optional<T> returned from this method does not contain a non-null value.
• <T> Optional<T> of(T value)
  Returns an Optional containing the specified value as the non-null value.
  If the specified value is null, it throws a NullPointerException.
• <T> Optional<T> ofNullable(T value)
  Returns an Optional containing the specified value if the value is non-null.
  If the specified value is null, it returns an empty Optional.

Example

The following code shows how to create Optional objects:

import java.util.Optional;
//from   w ww .  jav  a  2  s  .co m
public class Main {
  public static void main(String[] args) {
    Optional<String> empty  = Optional.empty();
    System.out.println(empty);

    Optional<String> str = Optional.of("java2s.com");
    System.out.println(str);

    String nullableString = ""; 
    Optional<String> str2  = Optional.of(nullableString);
    System.out.println(str2);
  }
}

The code above generates the following result.

Example 2

The following code prints the value in an Optional if it contains a non-null value:

import java.util.Optional;
//  ww w . ja v a 2  s . c o  m
public class Main {
  public static void main(String[] args) {
    Optional<String> str = Optional.of("java2s.com");

    if (str.isPresent()) {
      String value = str.get();
      System.out.println("Optional contains " + value);
    } else {
      System.out.println("Optional is  empty.");
    }
  }
}

The code above generates the following result.