Package org.apache.lucene.index

# Class IndexFileNames

java.lang.Object
org.apache.lucene.index.IndexFileNames

public final class IndexFileNames extends Object
This class contains useful constants representing filenames and extensions used by lucene, as well as convenience methods for querying whether a file name matches an extension (`matchesExtension`), as well as generating file names from a segment name, generation and extension ( `fileNameFromGeneration`, `segmentFileName`).

NOTE: extensions used by codecs are not listed here. You must interact with the `Codec` directly.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

## Field Summary

Fields
Modifier and Type
Field
Description
`static final Pattern`
`CODEC_FILE_PATTERN`
All files created by codecs much match this pattern (checked in SegmentInfo).
`static final String`
`PENDING_SEGMENTS`
Name of pending index segment file
`static final String`
`SEGMENTS`
Name of the index segment file

## Method Summary

Modifier and Type
Method
Description
`static String`
`fileNameFromGeneration(String base, String ext, long gen)`
Computes the full file name from base, extension and generation.
`static String`
`getExtension(String filename)`
Return the extension (anything after the first '.'), or null if there is no '.' in the file name.
`static boolean`
`matchesExtension(String filename, String ext)`
Returns true if the given filename ends with the given extension.
`static long`
`parseGeneration(String filename)`
Returns the generation from this file name, or 0 if there is no generation.
`static String`
`parseSegmentName(String filename)`
Parses the segment name out of the given file name.
`static String`
`segmentFileName(String segmentName, String segmentSuffix, String ext)`
Returns a file name that includes the given segment name, your own custom name and extension.
`static String`
`stripExtension(String filename)`
Removes the extension (anything after the first '.'), otherwise returns the original filename.
`static String`
`stripSegmentName(String filename)`
Strips the segment name out of the given file name.

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

## Field Details

### SEGMENTS

public static final String SEGMENTS
Name of the index segment file

See Also:
  - Constant Field Values

### PENDING_SEGMENTS

public static final String PENDING_SEGMENTS
Name of pending index segment file

See Also:
  - Constant Field Values

### CODEC_FILE_PATTERN

public static final Pattern CODEC_FILE_PATTERN
All files created by codecs much match this pattern (checked in SegmentInfo).

## Method Details

### fileNameFromGeneration

public static String fileNameFromGeneration(String base, String ext, long gen)
Computes the full file name from base, extension and generation. If the generation is -1, the file name is null. If it's 0, the file name is <base>.<ext>. If it's > 0, the file name is <base>_<gen>.<ext>.
NOTE: .<ext> is added to the name only if `ext` is not an empty string.

Parameters:
  `base` - main part of the file name
  `ext` - extension of the filename
  `gen` - generation

### segmentFileName

public static String segmentFileName(String segmentName, String segmentSuffix, String ext)
Returns a file name that includes the given segment name, your own custom name and extension. The format of the filename is: <segmentName>(_<name>)(.<ext>).

NOTE: .<ext> is added to the result file name only if `ext` is not empty.

NOTE: _<segmentSuffix> is added to the result file name only if it's not the empty string

NOTE: all custom files should be named using this method, or otherwise some structures may fail to handle them properly (such as if they are added to compound files).

### matchesExtension

public static boolean matchesExtension(String filename, String ext)
Returns true if the given filename ends with the given extension. One should provide a pure extension, without '.'.

### stripSegmentName

public static String stripSegmentName(String filename)
Strips the segment name out of the given file name. If you used `segmentFileName(java.lang.String, java.lang.String, java.lang.String)` or `fileNameFromGeneration(java.lang.String, java.lang.String, long)` to create your files, then this method simply removes whatever comes before the first '.', or the second '_' (excluding both).

Returns:
  the filename with the segment name removed, or the given filename if it does not contain a '.' and '_'.

### parseGeneration

public static long parseGeneration(String filename)
Returns the generation from this file name, or 0 if there is no generation.

### parseSegmentName

public static String parseSegmentName(String filename)
Parses the segment name out of the given file name.

Returns:
  the segment name only, or filename if it does not contain a '.' and '_'.

### stripExtension

public static String stripExtension(String filename)
Removes the extension (anything after the first '.'), otherwise returns the original filename.

### getExtension

public static String getExtension(String filename)
Return the extension (anything after the first '.'), or null if there is no '.' in the file name.