The Java Native Interface (JNI) is a native programming interface that is part of the Java Software Development Kit (SDK). JNI lets Java code use code and code libraries written in other languages, such as C and C++.The Invocation API, which is part of JNI, can be used to embed a Java virtual machine (JVM) into native applications, thereby allowing programmers to call Java code from within native code.his tutorial will walk you through the steps of using the Java Native Interface. You'll learn how to call native C/C++ code from within a Java application and how to call Java code from within a native C/C++ application.