In this tutorial, we will demonstrate the usage of the filter() and map() methods of the Optional class.

Optional filter() and map() Methods

filter() Method

If a value is present, and the value matches the given predicate, return an Optional describing the value, otherwise return an empty Optional.

import java.util.Optional;

public class OptionalDemo {
    public static void main(String[] args) {

        // without Optional
        String result = "abc";
        if(result != null && result.contains("abc")){
            System.out.println(result);
        }

        // with Optional
        Optional<String> optionalStr = Optional.of(result);
        optionalStr.filter(res -> res.contains("abc"))
                .ifPresent((res) -> System.out.println(res));
    }
}

Output:

abc
abc

map() Method

If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result.

import java.util.Optional;

public class OptionalDemo {
    public static void main(String[] args) {

        String result = " abc ";
        if(result != null && result.contains("abc")){
            System.out.println(result);
        }

        Optional<String> optionalStr = Optional.of(result);
        optionalStr.filter(res -> res.contains("abc"))
                .map(String::trim)
                .ifPresent((res) -> System.out.println(res));
    }
}

Output:

  abc
abc

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