文件夹目录中子文件夹的数量 [英] Number of subfolders in a folder directory

问题描述

我有一个包含数据文件（ .txt 等）和子文件夹的文件夹。

I have a folder which consists of both datafiles (.txt etc) and subfolders.

在Java中，我该如何完成获取任何指定目录路径中子文件夹的数量的操作？

In Java, how would I accomplish getting the number of subfolders in any specified directory path?

（因此不包括数据文件；仅对子文件夹进行计数）

(so excluding the datafiles; only counting the subfolders)

我已经读过有关计算 .txt 文件数量的信息，但似乎找不到关于仅计算子文件夹的信息。

I have read about counting the number of .txt files but can't seem to find anything about counting subfolders only.

我不知道从哪里开始，但给您一个想法：

I have no idea where to start but to give you an idea:

String directory = "C:\Users\ . \Desktop\ . \workspace\src\testfolder";
int numberOfSubfolders;

//what is numberOfSubfolders in testfolder?

感谢所有帮助。

推荐答案

您可以使用 FileFilter 仅列出目录：

You can use FileFilter to list only directories:

File file = new File("/tmp");
File[] files = file.listFiles(new FileFilter() {
    @Override
    public boolean accept(File f) {
        return f.isDirectory();
    }
});
System.out.println("Folders count: " + files.length);

Java File 类是综合设计模式，因此您必须实际询问实例是否是文件： isFile（）或如果它是目录 isDirectory（）。

Java File class is an example of the Composite Design Pattern, so you have to actually ask the instance if it's a file: isFile() or if it's a directory isDirectory().

如果您要计数目录，并且正在使用Java8。 Files.find 函数，可以以更简洁的方式（实际上是单行）执行相同的操作：

If you want to count directories, and you're using Java 8. Files.find function, can do the same thing in a more concise manner (practically one-liner):

long count = Files.find(
    Paths.get("/tmp"), 
    1,  // how deep do we want to descend
    (path, attributes) -> attributes.isDirectory()
).count() - 1; // '-1' because '/tmp' is also counted in

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