The role of native in java

native is a keyword in Java used to declare a method implemented in a non-Java environment (such as native code), mainly used to access system-level functionality, improve performance, and integrate existing code. The declaration syntax for native methods is: native <return_type> <method_name> (<parameters>). Implementing native methods requires using JNI (Java Native Interface) to bridge the Java virtual machine and native code.

The role of Native in Java

native is a keyword in the Java programming language that is used to Declare a method to be implemented in a non-Java environment (usually native code). Native methods allow Java programs to interact with the underlying operating system or other native libraries.

The role of native

native methods are mainly used for the following purposes:

• Access system-level functions:Java does not have direct access to some functions provided by the operating system, such as file system operations or network connections. Native methods can call platform-specific libraries or system calls to perform these tasks.
• Improve performance: For computationally intensive tasks, implementing the code in a more efficient language such as C or C and calling it as a native method can significantly improve performance.
• Integrate existing code: The native approach allows Java programs to integrate with existing non-Java libraries or code, thereby avoiding the need to reimplement existing functionality.

Declaration of native method

The native method is declared using the following syntax:

native <return_type> <method_name> (<parameters>);

where:

• <return_type> is the return value type of the method.
• <method_name> is the name of the method.
• <parameters> is the parameter list of the method.

Implement native methods

The native methods themselves are not implemented in Java code. Instead, they are bridged between the Java Virtual Machine (JVM) and native code by an interface called "JNI" (Java Native Interface). JNI provides a set of functions that allow Java programs to call native code and handle conversions between data types.

Example

The following example demonstrates how to use native methods to access system files:

public class FileAccess {

    // 声明 native 方法
    private native String readFile(String path);

    // 提供 native 方法的实现 (在 JNI 中)
    static {
        System.loadLibrary("fileaccess");
    }

    public static void main(String[] args) {
        FileAccess fileAccess = new FileAccess();
        String contents = fileAccess.readFile("test.txt");
        System.out.println(contents);
    }
}

In this example, readFile The method is declared native and is implemented by a native library called "fileaccess". When a Java program calls readFile, the JVM uses JNI to load the native library and calls its readFile function, which returns a string containing the contents of the file.

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