Java is mostly used as a server-side programming language to develop high-performance, low-latency servers capable of handling complicated operations. Java is widely used by investment banks to create end-to-end trading programs such as front-office apps for deal capture, middle-office applications for booking and allocation, and back-office applications for transmitting confirmations. Here is A list of the top 10 free and remunerated online Java courses in 2023, as well as a high-level best-starting course for object-oriented programming.

1. The Complete Java Course: It's an in-depth training with over 72 hours of content in which you'll learn everything a Java developer needs to know, including Core Java Fundamentals, data structures, OOP, Java Collections, Multithreading, File IO, Networking, Database, Java 8, Java 9 and Unit Testing improvements. You will not only study fundamentals, but also free Java development tools such as Eclipse, Maven, and others.
2. Certificate in Java Programming and Software Engineering Fundamentals from Coursera: The specialty includes four courses: Data Structure, Object Oriented Programming in Java, Advanced-Data Structure, and Mastering the Software Engineering Interview. All of the courses in this specialization are free to audit, but you must pay if you want a certificate, which is not a terrible offer. And, if you find Coursera courses beneficial, you should because they are made by well-known organizations and colleges from all over the world.
3. The Ultimate Java Programming Course For 2023: The course is also quite engaging, with quizzes, activities, and projects to help you remember what you've learned. This is the ideal way to learn because unless you use what you've learned by developing a project or addressing an issue, you'll forget it quickly. This training is intended specifically to avoid acquiring and forgetting patterns.
4. Java 17 Programming for Absolute Beginners: The course format is also excellent, with a step-by-step teaching style. Having taken some of the instructor's Spring courses in the past, I enjoy his approach and teaching manner. If you've completed a course, you'll be quite comfortable understanding and developing Java programs, and you'll be ready to take any Java interview if you're studying Java for a job.
5. Java Object-Oriented Programming Specialization: This Coursera Specialization is designed for aspiring software engineers who have some programming expertise in at least one other programming language and want to be able to address more sophisticated challenges using Java utilizing object-oriented architecture.

6. In-Depth Java: Become A Complete Java Engineer: The instructor knows a lot about Java, and his explanations are good, which makes studying more pleasant. This, like the prior Java course, is a very deep and comprehensive course that covers the bulk of Java subjects that a novice would like to learn.
7. Java Development Bootcamp in Its Entirety: This course also covers all of the fundamental Java subjects, such as variables, methods, control statements, loops, arrays, and Strings, object-oriented programming, file handling, database, multithreading, and collections.

8. Fundamentals of Java: The Java Programming Language: In short, a good course for learning Java from the ground up. It covers the whole Java programming language and servers used in all Java-based development activities.

9. Karpado's Java Professional Program: This Java Professional Program is excellent for aspiring Java developers. It's most likely the quickest method to become a well-paid full-stack Java developer. If you want to learn Java in-depth, this course is for you.
10. Java Programming: Using Software to Solve Problems: This is a fantastic Coursera course for learning to write in Java and boosting your programming and problem-solving abilities. You will learn how to create algorithms, as well as how to construct and debug applications. You will create programs that access and alter photos, webpages, and other forms of data using bespoke open-source classes.