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. ...

  Java 8 introduced several new features and enhancements: 1. Lambdas: Lambdas enable functional programming in Java and simplify the process of writing code that handles collections, concurrency, and other tasks. 2. Stream API: The Stream API is a new API for processing collections in a functional style, which makes it easy to filter, transform, and aggregate data. 3. Default Methods: Default methods allow interface evolution by providing a mechanism to add new methods to an interface without breaking the code that already implements the interface. 4. Date and Time API: The Date and Time API provides a more comprehensive and flexible API for working with dates and times. 5. Optional: Optional is a new class that helps avoid null pointer exceptions by providing a way to represent a value that may or may not be present. 6. Nashorn JavaScript Engine: Nashorn is a new JavaScript engine that allows developers to embed JavaScript in Java applications and execute it on the JVM. 7. Type A...