这是java的一个吸引力，使用短路或'||'，测试目录的存在，并为您制作目录

public File checkAndMakeTheDirectory() {
    File theDirectory = new File("/path/directory");
    if (theDirectory.exists() || theDirectory.mkdirs())
        System.out.println("The folder has been created or has been already there");
    return theDirectory;
}

如果If的第一部分为真，它不会运行第二部分，如果第一部分为假，它也会运行第二部分

对于java 7及以上版本:

Path path = Paths.get("/your/path/string");
Files.createDirectories(path);

在创建之前检查目录或文件是否存在似乎是不必要的，from createDirectories javadocs:

Creates a directory by creating all nonexistent parent directories first. Unlike the createDirectory method, an exception is not thrown if the directory could not be created because it already exists. The attrs parameter is optional file-attributes to set atomically when creating the nonexistent directories. Each file attribute is identified by its name. If more than one attribute of the same name is included in the array then all but the last occurrence is ignored. If this method fails, then it may do so after creating some, but not all, of the parent directories.

Mkdir vs mkdirs

如果要创建单个目录，请使用mkdir

new File("/path/directory").mkdir();

如果想要创建文件夹结构的层次结构，请使用mkdirs

 new File("/path/directory").mkdirs();

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");
        }
    }
}

new File("/path/directory").mkdirs();

这里的“directory”是你想要创建/存在的目录的名称。

这是java的一个吸引力，使用短路或'||'，测试目录的存在，并为您制作目录

public File checkAndMakeTheDirectory() {
    File theDirectory = new File("/path/directory");
    if (theDirectory.exists() || theDirectory.mkdirs())
        System.out.println("The folder has been created or has been already there");
    return theDirectory;
}

如果If的第一部分为真，它不会运行第二部分，如果第一部分为假，它也会运行第二部分