public class Test1 {
    public static void main(String[] args)
    {
       String path = System.getProperty("user.home");
       File dir=new File(path+"/new folder");
       if(dir.exists()){
           System.out.println("A folder with name 'new folder' is already exist in the path "+path);
       }else{
           dir.mkdir();
       }

    }
}

该功能允许在用户的主目录上创建新目录。

private static void createDirectory(final String directoryName) {
    final File homeDirectory = new File(System.getProperty("user.home"));
    final File newDirectory = new File(homeDirectory, directoryName);
    if(!newDirectory.exists()) {
        boolean result = newDirectory.mkdir();

        if(result) {
            System.out.println("The directory is created !");
        }
    } else {
        System.out.println("The directory already exist");
    }
}

虽然这个问题已经有了答案。我想多放点东西，比如。 如果存在与您试图创建的目录名称相同的文件，则会提示错误。为将来的访客准备的。

public static void makeDir()
{
    File directory = new File(" dirname ");
    if (directory.exists() && directory.isFile())
    {
        System.out.println("The dir with name could not be" +
        " created as it is a normal file");
    }
    else
    {
        try
        {
            if (!directory.exists())
            {
                directory.mkdir();
            }
            String username = System.getProperty("user.name");
            String filename = " path/" + username + ".txt"; //extension if you need one

        }
        catch (IOException e)
        {
            System.out.println("prompt for error");
        }
    }
}

在Java 7中，您可以使用Files.createDirectories()。

例如:

Files.createDirectories(Paths.get("/path/to/directory"));

创建单个目录。 新文件(C: \ \ Directory1) .mkdir (); 创建一个名为“Directory2”的目录及其所有子目录“Sub2″”和“Sub-Sub2″”。 新文件(“C: \ \ Directory2 \ \ Sub2 \ \ Sub-Sub2”).mkdirs ()

源码:这个完美的教程，你也找一个使用的例子。

public class Test1 {
    public static void main(String[] args)
    {
       String path = System.getProperty("user.home");
       File dir=new File(path+"/new folder");
       if(dir.exists()){
           System.out.println("A folder with name 'new folder' is already exist in the path "+path);
       }else{
           dir.mkdir();
       }

    }
}