Java 8 Optional

A new class Optional in java.util package used to represent a value is present or absent, its main purpose it to keep us away from too many null checks and NullPointerExceptions

Advantages of using Java 8 Optional :

1. No more NullPointerException at run-time.
2. Develop clean and neat APIs.
3. No more Boiler plate code.
4. Null checks are not required.

Various methods in Optional object

1. Code to retrieve the wrapped value using get API

Optional<String> opt = Optional.of("programmertoday");
String name = opt.get();

2. Basic Methods from Optional

Optional.ofNullable() method : returns a Non-empty Optional if a value present in the given object. Otherwise returns empty Optional.
Optional.empty() method : useful to create an empty Optional object.

import java.util.Optional;

public class OptionalBasicExample {
    public static void main(String[] args) {
        Optional<String> gender = Optional.of("MALE");
        String answer1 = "Yes";
        String answer2 = null;
        System.out.println("Non-Empty Optional:" + gender);
        System.out.println("Non-Empty Optional: Gender value : " + gender.get());
        System.out.println("Empty Optional: " + Optional.empty());
        System.out.println("ofNullable on Non-Empty Optional: " + Optional.ofNullable(answer1));
        System.out.println("ofNullable on Empty Optional: " + Optional.ofNullable(answer2));   // java.lang.NullPointerException   System.out.println("ofNullable on Non-Empty Optional: " +    Optional.of(answer2));     
       
        } }
        Output:
        Non - Empty Optional:
        Optional[MALE]
        Non - Empty Optional:
        Gender value :MALE
        Empty Optional:Optional.empty

        ofNullable on Non - Empty Optional:
        Optional[Yes]
        ofNullable on Empty Optional:Optional.empty

        Exception in thread "main" java.lang.NullPointerExceptio
        at java.util.Objects.requireNonNull(Objects.java:203)
        at java.util.Optional.<init> (Optional.java:96)
        at java.util.Optional.of(Optional.java:108)

3. Optional – map and flatMap methods

Optional.ofNullable() method returns a Non-empty Optional if a value present in the given object. Otherwise returns empty Optional.
Optionaal.empty() method is useful to create an empty Optional object.

import java.util.Optional;

public class OptionalMapFlatMapExample {
    public static void main(String[] args) {
        Optional<String> nonEmptyGender = Optional.of("male");
        Optional<String> emptyGender = Optional.empty();
        System.out.println("Non-Empty Optional:: " + nonEmptyGender.map(String::toUpperCase));
        System.out.println("Empty Optional    :: " + emptyGender.map(String::toUpperCase));
        Optional<Optional<String>> nonEmptyOtionalGender = Optional.of(Optional.of("male"));
        System.out.println("Optional value   :: " + nonEmptyOtionalGender);
        System.out.println("Optional.map     :: " + nonEmptyOtionalGender.map(gender -> gender.map(String::toUpperCase)));
        System.out.println("Optional.flatMap :: " + nonEmptyOtionalGender.flatMap(gender -> gender.map(String::toUpperCase)));
    }
}

Output:
        Non-Empty Optional::Optional[MALE]
        Empty Optional::Optional.empty
        Optional value::Optional[Optional[male]]
        Optional.map::Optional[Optional[MALE]]
        Optional.flatMap::Optional[MALE]

4. Optional – filter method

import java.util.Optional;

public class OptionalFilterExample {
    public static void main(String[] args) {
        Optional<String> gender = Optional.of("MALE");
        Optional<String> emptyGender = Optional.empty(); //Filter on Optional   
        System.out.println(gender.filter(g -> g.equals("male"))); //Optional.empty   
        System.out.println(gender.filter(g -> g.equalsIgnoreCase("MALE"))); //Optional[MALE]   
        System.out.println(emptyGender.filter(g -> g.equalsIgnoreCase("MALE"))); //Optional.empty   
        } 
}
        
Output:
        Optional.empty
        Optional[MALE]
        Optional.empty

5. Optional – isPresent and ifPresent methods

Optional.isPresent() returns true if the given Optional object is non-empty. Otherwise it returns false.
Optional.ifPresent() performs given action if the given Optional object is non-empty. Otherwise it returns false

import java.util.Optional;

public class OptionalIfPresentExample {
    public static void main(String[] args) {
        Optional<String> gender = Optional.of("MALE");
        Optional<String> emptyGender = Optional.empty();
        if (gender.isPresent()) {
            System.out.println("Value available.");
        } else {
            System.out.println("Value not available.");
        }
        gender.ifPresent(g -> System.out.println("In gender Option, value available."));   //condition failed, no output print   
        emptyGender.ifPresent(g -> System.out.println("In emptyGender Option, value available."));
    }
}

Output:
        Value available.
        In gender Option,value available.

6. Optional – orElse and orElseGet methods

It returns the value if present in Optional Container. Otherwise returns given default value.

import java.util.Optional;

public class OptionalOrElseExample {
    public static void main(String[] args) {
        Optional<String> gender = Optional.of("MALE");
        Optional<String> emptyGender = Optional.empty();
        System.out.println(gender.orElse("<N/A>")); //MALE   
        System.out.println(emptyGender.orElse("<N/A>")); //<N/A>   
        System.out.println(gender.orElseGet(() -> "<N/A>")); //MALE   
        System.out.println(emptyGender.orElseGet(() -> "<N/A>")); //<N/A>   
    }
}

Output:
        MALE
        <N/A>
        MALE
        <N /A>

Summary

In this article we learnt about Java 8 Optional package, its advantages and its variuos methods and implementations.
Hope you liked the article !

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