File Paths in Squirrel

Here’s the translation of the Go code to Java, formatted in Markdown for Hugo:

The java.nio.file.Paths class provides methods to work with file paths in a way that is portable between operating systems. For example, dir/file on Linux vs. dir\file on Windows.

import java.nio.file.Paths;
import java.nio.file.Path;
import java.io.File;

public class FilePaths {
    public static void main(String[] args) {
        // Paths.get() should be used to construct paths in a portable way.
        // It takes any number of arguments and constructs a hierarchical path from them.
        Path p = Paths.get("dir1", "dir2", "filename");
        System.out.println("p: " + p);

        // You should always use Paths.get() instead of concatenating
        // '/' or '\' manually. In addition to providing portability,
        // Paths.get() will also normalize paths by removing superfluous
        // separators and directory changes.
        System.out.println(Paths.get("dir1//", "filename"));
        System.out.println(Paths.get("dir1/../dir1", "filename"));

        // getParent() and getFileName() can be used to split a path to the
        // directory and the file.
        System.out.println("p.getParent(): " + p.getParent());
        System.out.println("p.getFileName(): " + p.getFileName());

        // We can check whether a path is absolute.
        System.out.println(Paths.get("dir/file").isAbsolute());
        System.out.println(Paths.get("/dir/file").isAbsolute());

        String filename = "config.json";

        // Some file names have extensions following a dot. We can split
        // the extension out of such names with getExtension().
        String ext = getExtension(filename);
        System.out.println(ext);

        // To find the file's name with the extension removed,
        // use substring.
        System.out.println(filename.substring(0, filename.length() - ext.length()));

        // Paths.relativize() finds a relative path between a base and a target.
        // It throws an IllegalArgumentException if the paths have different roots.
        try {
            Path base = Paths.get("a/b");
            Path target = Paths.get("a/b/t/file");
            Path rel = base.relativize(target);
            System.out.println(rel);

            target = Paths.get("a/c/t/file");
            rel = base.relativize(target);
            System.out.println(rel);
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        }
    }

    private static String getExtension(String filename) {
        int lastIndexOf = filename.lastIndexOf(".");
        if (lastIndexOf == -1) {
            return ""; // empty extension
        }
        return filename.substring(lastIndexOf);
    }
}

To run this program:

$ javac FilePaths.java
$ java FilePaths
p: dir1\dir2\filename
dir1\filename
dir1\filename
p.getParent(): dir1\dir2
p.getFileName(): filename
false
true
.json
config
t\file
..\c\t\file

Note that the output may vary slightly depending on the operating system, particularly in terms of path separators (\ on Windows, / on Unix-based systems).

In Java, we use the java.nio.file.Paths and java.nio.file.Path classes for most path operations. These provide similar functionality to Go’s filepath package. Some key differences:

Java uses Paths.get() instead of filepath.Join().
Path normalization happens automatically when you create a Path object.
Java’s getParent() and getFileName() methods are analogous to Go’s Dir() and Base().
Java doesn’t have a built-in method to get file extensions, so we defined a custom getExtension() method.
Java’s relativize() method is similar to Go’s Rel(), but it throws an exception instead of returning an error.

Remember that when working with file systems in Java, it’s generally best to use the java.nio.file package for better performance and more comprehensive file system interaction capabilities.

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File Paths in Squirrel