java-speed

  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 Annot

  JPA implemntation many to many parent child relation of using single table and one mapping table, with save api and fetch api by the root id. In JPA (Java Persistence API), a many-to-many relationship on a single class can be modeled using a self-referencing join table. This is done by creating two entities, one for the class and another for the join table, and using the @ManyToMany annotation on the class with the @JoinTable annotation on the join table. The @JoinTable annotation is used to specify the name and columns of the join table, and the @ManyToMany annotation is used to specify the mapping between the class and the join table. Here is an example of implementing a many-to-many parent-child relationship using JPA, with a Category table and a mapping table, as well as a save API and a fetch API by root ID: Create Category and Mapping entities. @Entity  public class Category { @Id@GeneratedValue(strategy = GenerationType.IDENTITY)   private Long id;   p