Shulou(Shulou.com)06/02 Report--

In this issue, the editor will bring you about what the Native method in Java is. The article is rich in content and analyzes and narrates it from a professional point of view. I hope you can get something after reading this article.

The following is the basic syntax for how to use the native method in java:

[public / protected / private] native [return-type] methodName ()

The above syntax shows how to declare native methods in java. Like a normal method, it needs to define an access modifier, followed by a native keyword, followed by the return type of the method, finally the method name, and, if necessary, input parameters.

How does the 1.Native method work in Java?

It can be defined as methods that are implemented in languages other than java, such as Cmax Cure +. The general idea behind using these methods may be to take advantage of the high performance or memory management provided in Chammer Candle +.

To support methods written in other languages, Java provides an interface called Java Native Interface, which acts as an intermediary between Java and other languages. The motivation for using JNI comes from the fact that it provides code reusability and high performance. It is important to note that code written in other languages, such as CCompact +, is not portable.

The following are the main components of the Java native native interface:

Javah: this is a tool provided in the java SDK that creates a C-compliant header file from an existing java file java class that contains native methods.

H: this is the header file provided in the Java Development Kit based on Java Candle +, and its function is to provide mapping between Java data types and native data types. The Javah file described above automatically generates this file.

Example of Native method in 2.Java

Now we will see an example that will clearly understand how the native method works in java. Here are the steps involved in using the native method:

1. Programming java code.

two。 Compile the java code.

3. Create a C header file.

4. The logic of native method is implemented in CumberCure +.

5. Create a shared library.

6. Run and test the java application.

The following example is divided into two parts: with java code and with native code.

Part 1: Java

Here is the java class that contains the native method.

Code:

Class NativeDemo {public native String encryptData (String inputdata); static {System.loadLibrary ("nativedemo"); / * lowercase of classname! * /} public static void main (String [] args) {NativeDemo demo = new NativeDemo (); System.out.println ("Encrypted data is" + demo.encryptData ("This is javakk"));}}

The above example contains the native method declared in the NativeDemo class. The implementation of the encryptData method is written in C. As you can see, we used a static block to load the encryptData method to implement the available native C library. An important thing to note is the string parameters provided in the system. The loadLibrary method is the lowercase name of the enclosing java class. Now, following the steps stated above, it's time to compile our java code.

The following command compiles the above java code.

Javac NativeDemo

Now in the next step, we will create a header file using the javah utility, as described below.

Javah-jni NativeDemo

The above command generates a javah file with the same name as the class name. This file will be included when writing a C implementation of the native method.

Part 2: C code

The following is the C implementation of the native function encryptData.

Code:

# include # include # include "NativeDemo.h" JNIEXPORT void JNICALLJava_NativeDemo_encryptData (JNIEnv * env, jobject obj, jstring inputstr) {const char * str= (* env)-> GetStringUTFChars (env,inputstr,0) / / create string from jstringchar Newch ='@'; for (I = 0; I NewStringUTF (str); / / convert string to jstring}

The above files are saved with NativeDemo.c

From the above code, we can see that the encryption logic is written in C language. This logic is simply based on replacing all vowels with @ and returning a string.

Compile the above C code

Use commands to compile code

The above command creates a shared library that is used by the java programming layer to invoke code written in C. We can use different compilation strategies depending on the compiler and the operating system.

After completing the above steps, we can call and run the java code as follows:

Java NativeDemo

If all goes well, you will see the following output:

Encrypted data is th@s @ s @ dailbc@ this is what the Native method in Java shared by the editor is. If you happen to have similar doubts, please refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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