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Build a Native Executable from a JAR File
/reference-manual/native-image/guides/build-native-executable-from-jar/

Build a Native Executable from a JAR File

You can build a native executable from a class file, from a JAR file, or from a module. This guide demonstrates how to build a native executable from a JAR file.

To build a native executable from a JAR file in the current working directory, use the following command:

native-image [options] -jar jarfile [executable name]

  1. Prepare the application.

    • Create a new Java project named "App", for example in your favorite IDE or from your terminal, with the following structure:

      | src
|   --com/
|      -- example
|          -- App.java

    • Add the following Java code to the src/com/example/App.java file:

      package com.example;

public class App {

    public static void main(String[] args) {
        String str = "Native Image is awesome";
        String reversed = reverseString(str);
        System.out.println("The reversed string is: " + reversed);
    }

    public static String reverseString(String str) {
        if (str.isEmpty())
            return str;
        return reverseString(str.substring(1)) + str.charAt(0);
    }
}

      This is a small Java application that reverses a String using recursion.

  2. Compile the application:

    javac -d build src/com/example/App.java

    This produces the file App.class in the build/com/example directory.

  3. Create a runnable JAR file:

    jar --create --file App.jar --main-class com.example.App -C build .

    It will generate a runnable JAR file, named App.jar, in the project root directory: To view its contents, run the command jar tf App.jar.

  4. Create a native executable:

    native-image -jar App.jar

    It will produce a native executable in the project root directory.

  5. Run the native executable:

    ./App

The default behavior of native-image is aligned with the java command which means you can pass the -jar, -cp, -m options to build with Native Image as you would normally do with java. For example, java -jar App.jar someArgument becomes native-image -jar App.jar and ./App someArgument.

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