ExtensionFileComparator

java.lang.Object
- org.apache.commons.io.comparator.ExtensionFileComparator

All Implemented Interfaces:

Serializable, Comparator<File>
```
public class ExtensionFileComparator
extends Object
implements Serializable
```
Compare the file name extensions for order (see FilenameUtils.getExtension(String)).
This comparator can be used to sort lists or arrays of files by their file extension either in a case-sensitive, case-insensitive or system dependent case sensitive way. A number of singleton instances are provided for the various case sensitivity options (using IOCase) and the reverse of those options.
Example of a case-sensitive file extension sort using the EXTENSION_COMPARATOR singleton instance:
```
       List<File> list = ...
       ((AbstractFileComparator) ExtensionFileComparator.EXTENSION_COMPARATOR).sort(list);
 
```
Example of a reverse case-insensitive file extension sort using the EXTENSION_INSENSITIVE_REVERSE singleton instance:
```
       File[] array = ...
       ((AbstractFileComparator) ExtensionFileComparator.EXTENSION_INSENSITIVE_REVERSE).sort(array);
 
```
Since:

1.4

See Also:

Serialized Form

Field Summary

Fields
Modifier and Type	Field and Description
`static Comparator<File>`	`EXTENSION_COMPARATOR` Case-sensitive extension comparator instance (see `IOCase.SENSITIVE`)
`static Comparator<File>`	`EXTENSION_INSENSITIVE_COMPARATOR` Case-insensitive extension comparator instance (see `IOCase.INSENSITIVE`)
`static Comparator<File>`	`EXTENSION_INSENSITIVE_REVERSE` Reverse case-insensitive extension comparator instance (see `IOCase.INSENSITIVE`)
`static Comparator<File>`	`EXTENSION_REVERSE` Reverse case-sensitive extension comparator instance (see `IOCase.SENSITIVE`)
`static Comparator<File>`	`EXTENSION_SYSTEM_COMPARATOR` System sensitive extension comparator instance (see `IOCase.SYSTEM`)
`static Comparator<File>`	`EXTENSION_SYSTEM_REVERSE` Reverse system sensitive path comparator instance (see `IOCase.SYSTEM`)

Constructor Summary

Constructors
Constructor and Description
`ExtensionFileComparator()` Construct a case sensitive file extension comparator instance.
`ExtensionFileComparator(IOCase caseSensitivity)` Construct a file extension comparator instance with the specified case-sensitivity.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`int`	`compare(File file1, File file2)` Compare the extensions of two files the specified case sensitivity.
`File[]`	`sort(File... files)` Sort an array of files.
`List<File>`	`sort(List<File> files)` Sort a List of files.
`String`	`toString()` String representation of this file comparator.

Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Comparator
comparing, comparing, comparingDouble, comparingInt, comparingLong, equals, naturalOrder, nullsFirst, nullsLast, reversed, reverseOrder, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

- Field Detail
  - EXTENSION_COMPARATOR
```
public static final Comparator<File> EXTENSION_COMPARATOR
```
    Case-sensitive extension comparator instance (see IOCase.SENSITIVE)
  - EXTENSION_REVERSE
```
public static final Comparator<File> EXTENSION_REVERSE
```
    Reverse case-sensitive extension comparator instance (see IOCase.SENSITIVE)
  - EXTENSION_INSENSITIVE_COMPARATOR
```
public static final Comparator<File> EXTENSION_INSENSITIVE_COMPARATOR
```
    Case-insensitive extension comparator instance (see IOCase.INSENSITIVE)
  - EXTENSION_INSENSITIVE_REVERSE
```
public static final Comparator<File> EXTENSION_INSENSITIVE_REVERSE
```
    Reverse case-insensitive extension comparator instance (see IOCase.INSENSITIVE)
  - EXTENSION_SYSTEM_COMPARATOR
```
public static final Comparator<File> EXTENSION_SYSTEM_COMPARATOR
```
    System sensitive extension comparator instance (see IOCase.SYSTEM)
  - EXTENSION_SYSTEM_REVERSE
```
public static final Comparator<File> EXTENSION_SYSTEM_REVERSE
```
    Reverse system sensitive path comparator instance (see IOCase.SYSTEM)
- Constructor Detail
  - ExtensionFileComparator
```
public ExtensionFileComparator()
```
    Construct a case sensitive file extension comparator instance.
  - ExtensionFileComparator
```
public ExtensionFileComparator(IOCase caseSensitivity)
```
    Construct a file extension comparator instance with the specified case-sensitivity.
    
    Parameters:
    
    caseSensitivity - how to handle case sensitivity, null means case-sensitive
- Method Detail
  - compare
```
public int compare(File file1,
                   File file2)
```
    Compare the extensions of two files the specified case sensitivity.
    
    Specified by:
    
    compare in interface Comparator<File>
    
    Parameters:
    
    file1 - The first file to compare
    
    file2 - The second file to compare
    
    Returns:
    
    a negative value if the first file's extension is less than the second, zero if the extensions are the same and a positive value if the first files extension is greater than the second file.
  - toString
```
public String toString()
```
    String representation of this file comparator.
    
    Returns:
    
    String representation of this file comparator
  - sort
```
public File[] sort(File... files)
```
    Sort an array of files.
    This method uses Arrays.sort(Object[], Comparator) and returns the original array.
    
    Parameters:
    
    files - The files to sort, may be null
    
    Returns:
    
    The sorted array
    
    Since:
    
    2.0
  - sort
```
public List<File> sort(List<File> files)
```
    Sort a List of files.
    This method uses Collections.sort(List, Comparator) and returns the original list.
    
    Parameters:
    
    files - The files to sort, may be null
    
    Returns:
    
    The sorted list
    
    Since:
    
    2.0

Class ExtensionFileComparator

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Comparator

Field Detail

EXTENSION_COMPARATOR

EXTENSION_REVERSE

EXTENSION_INSENSITIVE_COMPARATOR

EXTENSION_INSENSITIVE_REVERSE

EXTENSION_SYSTEM_COMPARATOR

EXTENSION_SYSTEM_REVERSE

Constructor Detail

ExtensionFileComparator

ExtensionFileComparator

Method Detail

compare

toString

sort

sort