Java 8 Optional Class

Java 8 Optional Class

New features in Java 8

The Optional class is a nullable container object. If the value is present, the Ispresent () method returns True, and the call to the Get () method returns the object.

Optional is a container: it can hold the value of type T, or just save null. Optional provides a number of useful methods so that we do not have to explicitly perform null-value detection.

The introduction of the Optional class is a good solution to null pointer exceptions.

class declaration

The following is a declaration of a java.util.optional<t> class:

public final class Optional<T> extends Object Class method

Serial Number	Method & Description
1	Static <T> optional<t> Empty () Returns an empty Optional instance.
2	Boolean equals (Object obj) Determines whether other objects are equal to Optional.
3	optional<t> filter (predicate<? Super <T> predicate) If the value exists and the value matches the given predicate, a optional is returned to describe the value, otherwise an empty optional is returned.
4	<U> optional<u> flatMap (function<? Super T,optional<u>> Mapper) If the value exists, returns a value based on the mapping method contained by the optional, otherwise returns an empty optional
5	T get () If you include this value in this optional, return the value, or throw an exception: Nosuchelementexception
6	int Hashcode () Returns a hash code that has a value that returns 0 if the value does not exist.
7	void Ifpresent (consumer<? Super T> Consumer) If the value exists then use that value to call consumer, otherwise do nothing.
8	Boolean isPresent () If the value is present, the method returns True, otherwise false is returned.
9	<U>Optional<U> map (function<? Super T,? Extends u> mapper) If the value is present, the provided mapping method, if returned non-null, returns a optional that describes the result.
10	Static <T> optional<t> of (T value) Returns a optional that specifies a non-null value.
11	Static <T> optional<t> ofnullable (T value) If non-null, returns the specified value that Optional describes, otherwise returns an empty Optional.
12	T OrElse (t other) If the value is present, return the value, otherwise return to other.
13	T orelseget (supplier<? extends t> other) If the value is present, return the value, otherwise trigger other and return the result of the other call.
14	<x extends throwable> T orelsethrow (supplier<? extends x> Exceptionsupplier) If the value exists, returns the contained value, otherwise throws an exception inherited by Supplier
15	String toString () Returns a optional non-empty string that is used to debug

Note: These methods are inherited from the Java.lang.Object class.

Optional instances

We can better understand the use of the Optional class by using the following examples:

Java8tester.java fileImport Java.Util.Optional;Public Class Java8tester { Public Static void Main(String Args[]){ Java8tester Java8tester=New Java8tester();Integer Value1=Null;Integer value2=New Integer(10);//Optional.ofnullable-Allow pass as null parameter Optional<Integer>A=Optional.Ofnullable(Value1);//Optional.of-Throws an exception if the passed argument is null NullPointerException Optional<Integer>B=Optional.Of(value2);System.Out.println(Java8tester.Sum(A,B));} Public Integer Sum(Optional<Integer>A,Optional<Integer>B){ //Optional.ispresent-Determine if a value exists System.Out.println("The first parameter value exists:"+A.IsPresent());System.Out.println("The second value of the parameter exists:"+B.IsPresent());//Optional.orelse-Returns the value if it exists, otherwise returns the default value Integer Value1=A.OrElse(New Integer (0) Span class= "Hl-code" >; //optional.get-get value, value needs to exist integer value2 = b. Getreturn value1 + value2; } } /span>

Execute the above script and the output is:

Java8tester.  Java8tester the first parameter value exists:false The second parameter value exists:true      

Java 8 Optional Class