JavaScript frameworks offer reusable components and structures to streamline the development process, allowing developers to build powerful web applications quickly. React, for example, focuses on building user interfaces, while Vue offers flexibility and ease of integration. Angular, on the other hand, is a complete framework for building complex applications. Each framework has its pros and cons, and the choice largely depends on the project's requirements. For instance, React might be the best choice for a fast, interactive interface, while Angular is great for full-scale enterprise applications.

Accessibility involves creating content that can be navigated and understood by users with various disabilities, including visual, auditory, and cognitive impairments. Techniques like using semantic HTML, providing text alternatives for images, and ensuring proper contrast ratios between text and background colors are crucial. Additionally, ensuring that your website is navigable via keyboard-only controls can significantly enhance accessibility. With laws like ADA and WCAG guidelines in place, it's becoming more important for developers and designers to prioritize accessibility in web projects.

SQL is a standardized language for managing databases and retrieving data. With SQL, you can perform operations like selecting data with `SELECT`, updating records with `UPDATE`, or deleting them with `DELETE`. Joins, such as `INNER JOIN` and `LEFT JOIN`, allow you to connect data from different tables. Knowing how to write complex queries to filter, group, and sort data efficiently can greatly improve database management. Understanding SQL can also help in optimizing database performance, especially when dealing with large datasets in enterprise systems.

Object-oriented programming (OOP) is a programming paradigm that revolves around objects, classes, and the relationships between them. Java, being an OOP language, relies on these concepts to build scalable applications. Inheritance allows classes to inherit properties and methods from other classes, while encapsulation hides the internal workings of a class from outside interference. Polymorphism enables objects to take on multiple forms, allowing flexibility in method usage. Abstraction, on the other hand, focuses on simplifying complex systems by exposing only the essential details. Mastering these concepts is key to writing efficient, maintainable code in Java.