Can you explain what Spring is and what it is used for in Java development?

Spring is a popular framework for developing applications in Java, which simplifies the creation of enterprise and web applications. The main tasks of Spring:

• Dependency Injection, which simplifies component wiring.
• Ensuring modularity and testability of code.
• Support for various modules, such as Spring MVC for web applications, Spring Data for database operations, Spring Security for security.

Spring allows creating scalable and maintainable applications, minimizing boilerplate code and simplifying configuration.

Example of using Spring to create a REST controller:

@RestController
public class HelloController {
    @GetMapping("/hello")
    public String sayHello() {
        return "Hello, Spring!";
    }
}