Embed Directive in Mercury

Here’s the translation of the Go embed directive example to Java, formatted in Markdown suitable for Hugo:

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class EmbedExample {
    // In Java, we can't embed files at compile time like in Go.
    // Instead, we'll read files at runtime.
    private static final String FILE_PATH = "folder/single_file.txt";
    private static final String FOLDER_PATH = "folder";

    public static void main(String[] args) throws IOException {
        // Read the contents of single_file.txt
        String fileString = readFile(FILE_PATH);
        byte[] fileByte = Files.readAllBytes(Paths.get(FILE_PATH));

        // Print out the contents of single_file.txt
        System.out.print(fileString);
        System.out.print(new String(fileByte));

        // Retrieve some files from the folder
        String content1 = readFile(FOLDER_PATH + "/file1.hash");
        System.out.print(content1);

        String content2 = readFile(FOLDER_PATH + "/file2.hash");
        System.out.print(content2);
    }

    private static String readFile(String filePath) throws IOException {
        return new String(Files.readAllBytes(Paths.get(filePath)));
    }
}

In Java, there isn’t a direct equivalent to Go’s embed directive, which allows embedding files into the binary at compile time. Instead, we typically read files at runtime. This example demonstrates how to achieve similar functionality by reading files from the file system.

Here’s an explanation of the key parts:

1. We define constants for the file paths we’ll be reading.

2. In the main method, we read the contents of single_file.txt into both a String and a byte[] array.

3. We print the contents of the file using both the String and byte[] versions.

4. We then read and print the contents of file1.hash and file2.hash from the folder directory.

5. The readFile method is a helper function that reads the contents of a file into a String.

To run this example, you would need to create the necessary files and folders:

$ mkdir -p folder
$ echo "hello java" > folder/single_file.txt
$ echo "123" > folder/file1.hash
$ echo "456" > folder/file2.hash

Then compile and run the Java program:

$ javac EmbedExample.java
$ java EmbedExample
hello java
hello java
123
456

Note that this Java version reads the files at runtime, which is different from Go’s compile-time embedding. If you need to package resources with your Java application, you might consider using resource files and the getResourceAsStream method, or packaging your application as a JAR file that includes the necessary files.