Share the usage of JAVA Optional class

Optional is defined as a container class in JAVA, or rather, a container with only one element is stored.

container object which may or may not contain a non-null value.

Optional class structure Optional properties

The Optional class contains two properties:

Class attribute: EMPTY Object attribute: value

The EMPTY attribute is used to store an Optional object with value null.
The value attribute is used to store non-null objects.

Optional method

Optional has two construction methods, both of which are modified by private.

 private Optional() { this.value = null;}private Optional(T value) { this.value = Objects.requireNonNull(value);}

The parameterless construction method is used to initialize EMPTY. Parameter constructor is used to initialize non-null objects.

Because the constructor is modified to be private, Optional can only call objects through class methods if it wants to instantiate. Optional provides three class methods.

empty: Returns the Optional object with value null of: Returns the value of non-null of Optional object of Nullable: The value of value returns the corresponding Optional object according to whether the parameter is null or not.

 public static<T> Optional<T> empty() { Optional<T> t = (Optional<T>) EMPTY; return t;}public static <T> Optional<T> of(T value) { return new Optional<>(value);}public static <T> Optional<T> ofNullable(T value) { return value == null ? empty() : of(value);}

Example method introduction