If else code execution with Optional class

Question

I was going through a tutorial of Optional class here - https://www.geeksforgeeks.org/java-8-optional-class/ which has the following

String[] words = new String[10];
Optional<String> checkNull = Optional.ofNullable(words[5]);
if (checkNull.isPresent()) {
    String word = words[5].toLowerCase();
    System.out.print(word);
} else{
    System.out.println("word is null");
}

I am trying to make it of less lines using ifPresent check of Optional as

Optional.ofNullable(words[5]).ifPresent(a -> System.out.println(a.toLowerCase()))

but not able to get the else part further

Optional.ofNullable(words[5]).ifPresent(a -> System.out.println(a.toLowerCase())).orElse();// doesn't work```

Is there a way to do it?

closet you'll come for java-8 would be System.out.println(Optional.ofNullable(words[5]).map(String::toLowerCase).orElse("Not Present")); — Kishore Bandi
– Kishore Bandi, Commented Jan 7, 2019 at 4:24
Note: I've tagged the question with Java-8 based on the link shared by you, feel free to discard or modify the edit. — Naman
– Naman, Commented Jan 7, 2019 at 4:35

Community · Accepted Answer · 2020-06-20 09:12:55Z

Java-9

Java-9 introduced ifPresentOrElse for something similar in implementation. You could use it as :

Optional.ofNullable(words[5])
        .map(String::toLowerCase) // mapped here itself
        .ifPresentOrElse(System.out::println,
                () -> System.out.println("word is null"));

Java-8

With Java-8, you shall include an intermediate Optional/String and use as :

Optional<String> optional = Optional.ofNullable(words[5])
                                    .map(String::toLowerCase);
System.out.println(optional.isPresent() ? optional.get() : "word is null");

which can also be written as :

String value = Optional.ofNullable(words[5])
                       .map(String::toLowerCase)
                       .orElse("word is null");
System.out.println(value);

or if you don't want to store the value in a variable at all, use:

System.out.println(Optional.ofNullable(words[5])
                           .map(String::toLowerCase)
                           .orElse("word is null"));

Ryuzaki L · Accepted Answer · 2019-03-07 13:00:31Z

4

For a bit to be more clear ifPresent will take Consumer as argument and return type is void, so you cannot perform any nested actions on this

public void ifPresent(Consumer<? super T> consumer)

If a value is present, invoke the specified consumer with the value, otherwise do nothing.

Parameters:

consumer - block to be executed if a value is present

Throws:

NullPointerException - if value is present and consumer is null

So instead of ifPreset() use map()

String result =Optional.ofNullable(words[5]).map(String::toLowerCase).orElse(null);

print Just to print

System.out.println(Optional.ofNullable(words[5]).map(String::toLowerCase).orElse(null));

edited Mar 7, 2019 at 13:00

answered Jan 7, 2019 at 4:36

Ryuzaki L

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Comments

Vishwa Ratna · Accepted Answer · 2019-01-07 04:32:45Z

3

If you are using java 9, you can use ifPresentOrElse() method::

https://docs.oracle.com/javase/9/docs/api/java/util/Optional.html#ifPresentOrElse-java.util.function.Consumer-java.lang.Runnable-

Optional.of(words[5]).ifPresentOrElse(
   value -> System.out.println(a.toLowerCase()),
   () -> System.out.println(null)
);

If Java 8 then look this great cheat sheet :

http://www.nurkiewicz.com/2013/08/optional-in-java-8-cheat-sheet.html

edited Jan 7, 2019 at 4:32

answered Jan 7, 2019 at 4:27

Vishwa Ratna

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