JNI - Android, Java Native Layer, Electro4u

Java Native Interface (JNI)

Java Native Interface (JNI) is a programming interface that allows Java code to interact with native code, which is code that is written in a language other than Java, such as C or C++. JNI is used to access hardware, improve performance, and use existing libraries.

To use JNI, you must first declare a native method in your Java code. A native method is a method that is implemented in native code, rather than in Java. To declare a native method, you use the native keyword. For example, the following code declares a native method called average():

public native double average(int x, int y);

Once you have declared a native method, you must provide an implementation for the method in a native library. A native library is a file that contains native code. To create a native library, you can use a compiler for the language that you are using to write the native code.

Once you have created a native library, you can load it into the Java Virtual Machine (JVM) using the System.loadLibrary() method. For example, the following code loads a native library called libmyjni.so:

System.loadLibrary("libmyjni.so");

Once you have loaded a native library, you can call the native methods in the library from your Java code. To call a native method, you use the System.invokeNative() method. For example, the following code calls the average() method from the libmyjni.so library:

double average = (double)System.invokeNative("average", new Object[] { 10, 20 });

JNI is a powerful tool that can be used to extend the capabilities of Java. However, it is important to note that JNI can be complex and error-prone. If you are not familiar with JNI, it is best to consult a Java Native Interface tutorial before attempting to use it.

Here are some of the benefits of using JNI:

• Access hardware: JNI can be used to access hardware that is not directly accessible from Java, such as graphics cards, sound cards, and network interfaces.
• Improve performance: JNI can be used to improve the performance of Java applications by calling native code that is specifically optimized for the underlying hardware.
• Use existing libraries: JNI can be used to use existing libraries that are written in languages other than Java.

Here are some of the drawbacks of using JNI:

• Complexity: JNI can be complex and error-prone.
• Portability: JNI can be platform-specific, which means that code that uses JNI may not be portable to other platforms.
• Security: JNI can be used to bypass security restrictions in the JVM