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).

Class Summary

Class	Description
CompositeFileComparator	Compare two files using a set of delegate file Comparator.
DefaultFileComparator	Compare two files using the default File.compareTo(File) method.
DirectoryFileComparator	Compare two files using the File.isDirectory() method.
ExtensionFileComparator	Compare the file name extensions for order (see FilenameUtils.getExtension(String)).
LastModifiedFileComparator	Compare the last modified date/time of two files for order (see FileUtils.lastModifiedUnchecked(File)).
NameFileComparator	Compare the names of two files for order (see File.getName()).
PathFileComparator	Compare the path of two files for order (see File.getPath()).
SizeFileComparator	Compare the length/size of two files for order (see File.length() and FileUtils.sizeOfDirectory(File)).