The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
A few useful methods did not fit elsewhere in this lesson and are covered here. This section covers the following:
To determine the MIME type of a file, you might find the
probeContentType(Path)
method useful. For example:
try { String type = Files.probeContentType(filename); if (type == null) { System.err.format("'%s' has an" + " unknown filetype.%n", filename); } else if (!type.equals("text/plain") { System.err.format("'%s' is not" + " a plain text file.%n", filename); continue; } } catch (IOException x) { System.err.println(x); }
Note that probeContentType
returns null if the content type cannot be determined.
The implementation of this method is highly platform specific and is not infallible. The content type is determined by the platform's default file type detector. For example, if the detector determines a file's content type to be application/x-java
based on the .class
extension, it might be fooled.
You can provide a custom
FileTypeDetector
if the default is not sufficient for your needs.
The
example uses the Email
probeContentType
method.
To retrieve the default file system, use the
getDefault
method. Typically, this FileSystems
method (note the plural) is chained to one of the FileSystem
methods (note the singular), as follows:
PathMatcher matcher = FileSystems.getDefault().getPathMatcher("glob:*.*");
The path separator for POSIX file systems is the forward slash, /
, and for Microsoft Windows is the backslash, \
. Other file systems might use other delimiters. To retrieve the Path
separator for the default file system, you can use one of the following approaches:
String separator = File.separator; String separator = FileSystems.getDefault().getSeparator();
The
getSeparator
method is also used to retrieve the path separator for any available file system.
A file system has one or more file stores to hold its files and directories. The file store represents the underlying storage device. In UNIX operating systems, each mounted file system is represented by a file store. In Microsoft Windows, each volume is represented by a file store: C:
, D:
, and so on.
To retrieve a list of all the file stores for the file system, you can use the
getFileStores
method. This method returns an Iterable
, which allows you to use the
enhanced for statement to iterate over all the root directories.
for (FileStore store: FileSystems.getDefault().getFileStores()) { ... }
If you want to retrieve the file store where a particular file is located, use the
getFileStore
method in the Files
class, as follows:
Path file = ...; FileStore store= Files.getFileStore(file);
The
DiskUsage
example uses the getFileStores
method.