Native methods are Java™ methods that start in a language other than Java. Native methods can access system-specific functions and APIs that are not available directly in Java.
The use of native methods limits the portability of an application, because it involves system-specific code. Native methods can either be new native code statements or native code statements that call existing native code.
Once you decide that a native method is required, it may have to interoperate with the Java virtual machine where it runs. The Java Native Interface (JNI) facilitates this interoperability in a platform-neutral way.
The JNI is a set of interfaces that permit a native method to interoperate with the Java virtual machine in numerous ways. For example, the JNI includes interfaces that create new objects and call methods, get fields and set fields, process exceptions, and manipulate strings and arrays.
For a complete description of the JNI, refer to the Java Native Interface by Sun Microsystems, Inc., or The Source for Java Technology java.sun.com .