java-speed

 In Spring Data repositories, the relationship between repository methods and `Optional` can vary depending on the specific use case and method signature. 1 . `Optional` as a return type:    When a repository method is defined to return a single entity or an optional result, you can use the `Optional` type as the return type. This indicates that the method may or may not find a matching entity in the database.    Example:    ```java    Optional<YourEntity> findById(Long id);    ```    In this case, the `findById` method is defined to return an `Optional<YourEntity>`. If the entity exists in the database, the `Optional` will contain the entity. Otherwise, it will be empty. 2. `Optional` as a parameter type:    You can also use `Optional` as a parameter type to indicate an optional input value for a repository method. This allows you to handle scenarios where a parameter may or may not be present.    Example:    ```java    List<YourEntity> findByCategory(Optional<Str

Java 17, released in September 2021, introduced several new features and enhancements. While some of the most prominent changes in Java 17 have received widespread attention, here's a lesser-known unique feature: 1. Sealed Classes: Sealed classes are a feature that allows developers to control the extent to which other classes can inherit from them. By declaring a class as sealed, you can specify which other classes are allowed to subclass it. This feature enhances encapsulation and provides more control over class hierarchies and extensions. Sealed classes are declared using the `sealed` keyword, and the permitted subclasses are specified using the `permits` keyword. By default, a sealed class allows subclasses only from within the same module. However, you can also explicitly specify other modules that are permitted to subclass the sealed class. This feature enables developers to create more secure and maintainable code by restricting inheritance to a defined set of classes, prev