What is Optional in Java 8?

Deepika Sahu answered on December 17, 2022 Popularity 9/10 Helpfulness 2/10

answer What is Optional in Java 8?

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What is Optional in Java 8?

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Optional is a container object which is used to contain not-null objects.
An optional object is used to represent null with an absent value. 
The Optional class has various utility methods to facilitate code to handle values as 'available' or 'not available' instead of checking null values. 
The purpose of the Optional class is to provide a type-level solution for representing optional values instead of using null references.

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Contributed on Dec 17 2022

Deepika Sahu

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What is Optional in Java 8?

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import java.util.Optional;

public class OptionalClassExamples {

    public static void main(String[] args) {
        isPresentOptionalAPI();
        createEmptyOptionalObject();
        createEmptyOptionalObjectWithStaticAPI();
        ifPresentOptionalAPI();
        orElseOptionalAPI();
        orElseOptionalAPI();
        orElseGetOptionalAPI();
        orElseThrowOptionalAPI();
        getOptionalAPI();
    }

    // Returns an Optional with the specified present non-null value.
    private static void isPresentOptionalAPI() {
        Optional < String > opt = Optional.of("Ramesh");
        System.out.println(opt.isPresent());
    }

    // Returns an Optional with the specified present non-null value.
    private static void createEmptyOptionalObject() {
        Optional < String > empty = Optional.empty();
        System.out.println(empty.isPresent());

        // Optional object with the static of API:
        String name = "Ramesh";
        Optional.of(name);
    }

    private static void createEmptyOptionalObjectWithStaticAPI() {
        String name = "baeldung";
        Optional.of(name);
    }

// If a value is present, invoke the specified consumer with the value, otherwise do
// nothing.
    private static void ifPresentOptionalAPI() {
   // The ifPresent API enables us to run some code on the wrapped value if it is
        // found to be non-null.
        // Before Optional, we would do something like this:
        String name = "Ramesh";
        if (name != null) {
            System.out.println(name.length());
        }

        Optional < String > opt = Optional.of("Ramesh");
        opt.ifPresent(str -> System.out.println(str.length()));
    }

// If a value is present, invoke the specified consumer with the value, otherwise do
 // nothing.
    private static void orElseOptionalAPI() {
  // With orElse, the wrapped value is returned if it is present and the argument
   // given to
  // orElse is returned if the wrapped value is absent
        String nullName = null;

  // If a value is present, invoke the specified consumer with the value, otherwise
     // do nothing.
        //
        String name = Optional.ofNullable(nullName).orElse("Ramesh");
        System.out.println(name);
    }

    private static void orElseGetOptionalAPI() {
        String nullName = null;
        String name = Optional.ofNullable(nullName).orElseGet(() -> "Ramesh");
        System.out.println(name);
    }
    private static void orElseThrowOptionalAPI() {

        // This will throw exception
        String nullName = null;
        String name = Optional.ofNullable(nullName)
            .orElseThrow(IllegalArgumentException::new);
        System.out.println(name);
    }

    private static void getOptionalAPI() {
        Optional < String > opt = Optional.of("Ramesh");
        String name = opt.get();
        System.out.println(name);
    }

}

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Tags: java

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Contributed on Dec 17 2022

Deepika Sahu

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What is Optional in Java 8?

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