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## org.apache.lucene.index
Class IndexCommit

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

All Implemented Interfaces:
  IndexCommitPoint

    public abstract class IndexCommit

extends Object
implements IndexCommitPoint

Expert: represents a single commit into an index as seen by the `IndexDeletionPolicy` or `IndexReader`.

Changes to the content of an index are made visible only after the writer who made that change commits by writing a new segments file (`segments_N`). This point in time, when the action of writing of a new segments file to the directory is completed, is an index commit.

Each index commit point has a unique segments file associated with it. The segments file associated with a later index commit point would have a larger N.

WARNING: This API is a new and experimental and may suddenly change.

Constructor Summary
`IndexCommit()`

Method Summary
`void` | `delete()` Delete this commit point.
`boolean` | `equals(Object other)` Two IndexCommits are equal if both their Directory and versions are equal.
`abstract Directory` | `getDirectory()` Returns the `Directory` for the index.
`abstract Collection` | `getFileNames()` Returns all index files referenced by this commit point.
`long` | `getGeneration()` Returns the generation (the _N in segments_N) for this IndexCommit
`abstract String` | `getSegmentsFileName()` Get the segments file (`segments_N`) associated with this commit point.
`long` | `getTimestamp()` Convenience method that returns the last modified time of the segments_N file corresponding to this index commit, equivalent to getDirectory().fileModified(getSegmentsFileName()).
`long` | `getVersion()` Returns the version for this IndexCommit.
`int` | `hashCode()`
`boolean` | `isDeleted()`
`boolean` | `isOptimized()` Returns true if this commit is an optimized index.

Methods inherited from class java.lang.Object
`clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### IndexCommit

    public IndexCommit()

Method Detail

### getSegmentsFileName

    public abstract String getSegmentsFileName()

  Get the segments file (`segments_N`) associated with this commit point.

  Specified by:
    `getSegmentsFileName` in interface `IndexCommitPoint`

### getFileNames

    public abstract Collection getFileNames()
                                     throws IOException

  Returns all index files referenced by this commit point.

  Specified by:
    `getFileNames` in interface `IndexCommitPoint`
  Throws:
    `IOException`

### getDirectory

    public abstract Directory getDirectory()

  Returns the `Directory` for the index.

### delete

    public void delete()

  Delete this commit point. This only applies when using the commit point in the context of IndexWriter's IndexDeletionPolicy.

  Upon calling this, the writer is notified that this commit point should be deleted.

  Decision that a commit-point should be deleted is taken by the `IndexDeletionPolicy` in effect and therefore this should only be called by its `onInit()` or `onCommit()` methods.

  Specified by:
    `delete` in interface `IndexCommitPoint`

### isDeleted

    public boolean isDeleted()

### isOptimized

    public boolean isOptimized()

  Returns true if this commit is an optimized index.

### equals

    public boolean equals(Object other)

  Two IndexCommits are equal if both their Directory and versions are equal.

  Overrides:
    `equals` in class `Object`

### hashCode

    public int hashCode()

  Overrides:
    `hashCode` in class `Object`

### getVersion

    public long getVersion()

  Returns the version for this IndexCommit. This is the same value that `IndexReader.getVersion()` would return if it were opened on this commit.

### getGeneration

    public long getGeneration()

  Returns the generation (the _N in segments_N) for this IndexCommit

### getTimestamp

    public long getTimestamp()
                      throws IOException

  Convenience method that returns the last modified time of the segments_N file corresponding to this index commit, equivalent to getDirectory().fileModified(getSegmentsFileName()).

  Throws:
    `IOException`

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