Package org.apache.commons.io.comparator

This package provides various Comparator implementations for Files.

Sorting

All the compartors include convenience utility sort(File...) and sort(List) methods.

For example, to sort the files in a directory by name:

        File[] files = dir.listFiles();
        NameFileComparator.NAME_COMPARATOR.sort(files);
  

...alternatively you can do this in one line:

        File[] files = NameFileComparator.NAME_COMPARATOR.sort(dir.listFiles());
  

Composite Comparator

The CompositeFileComparator can be used to compare (and sort lists or arrays of files) by combining a number other comparators.

For example, to sort an array of files by type (i.e. directory or file) and then by name:

        CompositeFileComparator comparator =
                        new CompositeFileComparator(
                                    DirectoryFileComparator.DIRECTORY_COMPARATOR,
                                    NameFileComparator.NAME_COMPARATOR);
        File[] files = dir.listFiles();
        comparator.sort(files);
  

Singleton Instances (thread-safe)

The Comparator implementations have some convenience singleton(thread-safe) instances ready to use:

• DefaultFileComparator - default file compare:
  • DEFAULT_COMPARATOR - Compare using File.compareTo(File) method.
  • DEFAULT_REVERSE - Reverse compare of File.compareTo(File) method.
• DirectoryFileComparator - compare by type (directory or file):
  • DIRECTORY_COMPARATOR - Compare using File.isDirectory() method (directories < files).
  • DIRECTORY_REVERSE - Reverse compare of File.isDirectory() method (directories > files).
• ExtensionFileComparator - compare file extenstions:
  • EXTENSION_COMPARATOR - Compare using FilenameUtils.getExtension(String) method.
  • EXTENSION_REVERSE - Reverse compare of FilenameUtils.getExtension(String) method.
  • EXTENSION_INSENSITIVE_COMPARATOR - Case-insensitive compare using FilenameUtils.getExtension(String) method.
  • EXTENSION_INSENSITIVE_REVERSE - Reverse case-insensitive compare of FilenameUtils.getExtension(String) method.
  • EXTENSION_SYSTEM_COMPARATOR - System sensitive compare using FilenameUtils.getExtension(String) method.
  • EXTENSION_SYSTEM_REVERSE - Reverse system sensitive compare of FilenameUtils.getExtension(String) method.
• LastModifiedFileComparator - compare the file's last modified date/time:
  • LASTMODIFIED_COMPARATOR - Compare using File.lastModified() method.
  • LASTMODIFIED_REVERSE - Reverse compare of File.lastModified() method.
• NameFileComparator - compare file names:
  • NAME_COMPARATOR - Compare using File.getName() method.
  • NAME_REVERSE - Reverse compare of File.getName() method.
  • NAME_INSENSITIVE_COMPARATOR - Case-insensitive compare using File.getName() method.
  • NAME_INSENSITIVE_REVERSE - Reverse case-insensitive compare of File.getName() method.
  • NAME_SYSTEM_COMPARATOR - System sensitive compare using File.getName() method.
  • NAME_SYSTEM_REVERSE - Reverse system sensitive compare of File.getName() method.
• PathFileComparator - compare file paths:
  • PATH_COMPARATOR - Compare using File.getPath() method.
  • PATH_REVERSE - Reverse compare of File.getPath() method.
  • PATH_INSENSITIVE_COMPARATOR - Case-insensitive compare using File.getPath() method.
  • PATH_INSENSITIVE_REVERSE - Reverse case-insensitive compare of File.getPath() method.
  • PATH_SYSTEM_COMPARATOR - System sensitive compare using File.getPath() method.
  • PATH_SYSTEM_REVERSE - Reverse system sensitive compare of File.getPath() method.
• SizeFileComparator - compare the file's size:
  • SIZE_COMPARATOR - Compare using File.length() method (directories treated as zero length).
  • LASTMODIFIED_REVERSE - Reverse compare of File.length() method (directories treated as zero length).
  • SIZE_SUMDIR_COMPARATOR - Compare using FileUtils.sizeOfDirectory(File) method (sums the size of a directory's contents).
  • SIZE_SUMDIR_REVERSE - Reverse compare of FileUtils.sizeOfDirectory(File) method (sums the size of a directory's contents).