A Beginner’s Guide to Java Native Interface

Java Native Interface allows Java code running on the JVM to call native applications and libraries written in languages such as C or C++.

public class NativeHello {
  static {
    System.loadLibrary("nativehello");
  }

  private native void sayHello();

  public static void main(String[] args) {
    new NativeHello().sayHello();
  }
}

JNI is useful when you need to integrate with platform-specific APIs or reuse existing native libraries.