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## org.apache.lucene.analysis
Class CharFilter

    java.lang.Object
      java.io.Reader
          org.apache.lucene.analysis.CharFilter

All Implemented Interfaces:
  Closeable, Readable

    public abstract class CharFilter

extends Reader

Subclasses of CharFilter can be chained to filter a Reader They can be used as `Reader` with additional offset correction. `Tokenizer`s will automatically use `correctOffset(int)` if a CharFilter subclass is used.

This class is abstract: at a minimum you must implement `Reader.read(char[], int, int)`, transforming the input in some way from `input`, and `correct(int)` to adjust the offsets to match the originals.

You can optionally provide more efficient implementations of additional methods like `Reader.read()`, `Reader.read(char[])`, `Reader.read(java.nio.CharBuffer)`, but this is not required.

For examples and integration with `Analyzer`, see the `Analysis package documentation`.

Field Summary
`protected Reader` | `input` The underlying character-input stream.

Fields inherited from class java.io.Reader
`lock`

Constructor Summary
`CharFilter(Reader input)` Create a new CharFilter wrapping the provided reader.

Method Summary
`void` | `close()` Closes the underlying input stream.
`protected abstract int` | `correct(int currentOff)` Subclasses override to correct the current offset.
`int` | `correctOffset(int currentOff)` Chains the corrected offset through the input CharFilter(s).

Methods inherited from class java.io.Reader
`mark, markSupported, read, read, read, read, ready, reset, skip`

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

Field Detail

### input

    protected final Reader input

  The underlying character-input stream.

Constructor Detail

### CharFilter

    public CharFilter(Reader input)

  Create a new CharFilter wrapping the provided reader.

  Parameters:
    `input` - a Reader, can also be a CharFilter for chaining.

Method Detail

### close

    public void close()
               throws IOException

  Closes the underlying input stream.

  NOTE: The default implementation closes the input Reader, so be sure to call `super.close()` when overriding this method.

  Specified by:
    `close` in interface `Closeable`
  Specified by:
    `close` in class `Reader`
  Throws:
    `IOException`

### correct

    protected abstract int correct(int currentOff)

  Subclasses override to correct the current offset.

  Parameters:
    `currentOff` - current offset
  Returns:
    corrected offset

### correctOffset

    public final int correctOffset(int currentOff)

  Chains the corrected offset through the input CharFilter(s).

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