What functions does the Optional class in Java have?

The Optional class in Java has the following features:

1. Provided is a container type that can be used to package values that might be empty.
2. Optional objects can be created using static methods, such as Optional.of(value) and Optional.ofNullable(value).
3. You can use the isPresent() method to check if an Optional object contains a value, and use the get() method to retrieve the wrapped value.
4. You can specify a default value using the orElse(value) method, which will be returned when the Optional object is empty.
5. You can specify an implementation of the Supplier interface to provide a default value using the orElseGet(Supplier supplier) method.
6. You can use the orElseThrow(Supplier exceptionSupplier) method to throw a specified exception when the Optional object is empty.
7. You can use the ifPresent(Consumer consumer) method to check if an Optional object contains a value, and apply the specified implementation of the Consumer interface to handle the value when present.
8. The filter method can be used to filter the value of an Optional object using a Predicate and returns a new Optional object.
9. You can use the map method to map the value of an Optional object with a specified function and return a new Optional object.
10. The flatMap method can be used to map the value of an Optional object using a function, and return a new Optional object. If the mapping result is Optional.empty(), then an empty Optional object is returned.
11. Can you explain that to me one more time?
12. You can use the orElseThrow() method to throw a NoSuchElementException when the Optional object is empty.
13. The equals() method can be used to determine if two Optional objects are equal.
14. You can obtain the hash code of an Optional object using the hashCode() method.
15. The Optional object can be converted to a string representation using the toString() method.

By using the Optional class, you can effectively handle values that may be empty, reduce the occurrence of null pointer exceptions, and improve the readability and robustness of the code.