Java is a popular, general-purpose programming language. It is designed to be secure and efficient, and is used for everything from web applications to mobile applications. Java is an object-oriented language, and has a robust set of libraries and frameworks for creating complex applications. Java is also designed to be cross-platform, and can be used to create applications that can work across different platforms.
Together, React + Java provides an effective platform for developing large-scale applications. React and Java both provide powerful frameworks and libraries for creating complex applications, and their combination allows developers to quickly create sophisticated user interfaces and powerful applications.