# java(Kotlin語法) 檔案讀寫、資料夾創建

### nio是non-blocking比io新速度也比較快，也不會需要等待暫停等待資料到達
可以使用`System.getProperty("user.dir")`來查詢[當前目錄](https://github.com/EriaWist/My_Article/blob/main/Java/%E7%B3%BB%E7%B5%B1%E7%9B%B8%E9%97%9C%E8%B3%87%E8%A8%8A%E5%8F%96%E5%BE%97%E6%96%B9%E6%B3%95.md)</br>
關於使用File在`Mac`與`Windows`的路徑會自動轉換[文件](https://stackoverflow.com/questions/2417485/difference-between-file-separator-and-slash-in-paths)

With the Java libraries for dealing with files, you can safely use / (slash, not backslash) on all platforms. The library code handles translating things into platform-specific paths internally.

使用nio的方式
> 關於使用`path.of` or `paths.get` [連結](https://stackoverflow.com/questions/58631724/paths-get-vs-path-of) [文件](https://docs.oracle.com/en/java/javase/13/docs/api/java.base/java/nio/file/Paths.html)

API Note:
It is recommended to obtain a Path via the Path.of methods instead of via the get methods defined in this class as this class may be deprecated in a future release.

結論用`path.of`
可以用

    val fileName =  Path.of("teww/a123/demo.txt");
    fileName.createDirectory()

但是Kotlin[警告](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.io.path/-experimental-path-api/)

This annotation marks the extensions and top-level functions for working with java.nio.file.Path considered experimental.

等未來穩定在更新

---

使用io的方式 [參考文件](https://www.w3schools.com/java/java_files_create.asp)
> 創立資料夾

  var file = File("test/123")
  file.mkdirs()

> 在創立的資料夾內新增檔案

var file = File("test/123/filename.txt")
file.createNewFile()

> 寫入檔案

var myWriter =  FileWriter("filename.txt");
myWriter.write("Files in Java might be tricky, but it is fun enough!");
myWriter.close();

> 讀取檔案

var file = File("test/123/filename.txt")
var myReader =  Scanner(file);
while (myReader.hasNextLine()) {
    var data = myReader.nextLine();
    println(data);
}
myReader.close();

> 刪除檔案

var file = File("test/123/filename.txt")
file.delete()