Java Native Interface (JNI) is a framework in Java that enables Java code to interact with code written in other programming languages such as C, C++, and assembly language. JNI is a way to use native libraries, which typically provide access to hardware or OS-specific functionality that is not available in the Java environment.

With JNI, Java code can call functions defined in a native library or shared object and pass data between Java objects and C structures. JNI provides mechanisms for managing memory allocation and deallocation in both Java and C memory spaces.

JNI can be useful in a number of scenarios, such as when working with legacy C or C++ code or when accessing hardware-specific functionality. Some common use cases for JNI include multimedia processing, image processing, and gaming.

When working with JNI, it is important to ensure that the native code is compiled correctly and linked with the Java code properly. Additionally, developers need to consider security and performance issues when using JNI, as it can introduce vulnerabilities and overhead.

Overall, JNI provides a way for Java code to access native libraries and leverage the capabilities of other programming languages, making Java a versatile and powerful language for a wide range of applications.