org.apache.lucene.analysis.position
Class PositionFilter

java.lang.Object
  extended by org.apache.lucene.util.AttributeSource
      extended by org.apache.lucene.analysis.TokenStream
          extended by org.apache.lucene.analysis.TokenFilter
              extended by org.apache.lucene.analysis.position.PositionFilter
All Implemented Interfaces:
Closeable

public final class PositionFilter
extends TokenFilter

Set the positionIncrement of all tokens to the "positionIncrement", except the first return token which retains its original positionIncrement value. The default positionIncrement value is zero.


Nested Class Summary
 
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.AttributeFactory, AttributeSource.State
 
Field Summary
 
Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
 
Constructor Summary
PositionFilter(TokenStream input)
          Constructs a PositionFilter that assigns a position increment of zero to all but the first token from the given input stream.
PositionFilter(TokenStream input, int positionIncrement)
          Constructs a PositionFilter that assigns the given position increment to all but the first token from the given input stream.
 
Method Summary
 boolean incrementToken()
          Consumers (i.e., IndexWriter) use this method to advance the stream to the next token.
 void reset()
          Reset the filter as well as the input TokenStream.
 
Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end
 
Methods inherited from class org.apache.lucene.util.AttributeSource
addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Constructor Detail

PositionFilter

public PositionFilter(TokenStream input)
Constructs a PositionFilter that assigns a position increment of zero to all but the first token from the given input stream.

Parameters:
input - the input stream

PositionFilter

public PositionFilter(TokenStream input,
                      int positionIncrement)
Constructs a PositionFilter that assigns the given position increment to all but the first token from the given input stream.

Parameters:
input - the input stream
positionIncrement - position increment to assign to all but the first token from the input stream
Method Detail

incrementToken

public final boolean incrementToken()
                             throws IOException
Description copied from class: TokenStream
Consumers (i.e., IndexWriter) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriate AttributeImpls with the attributes of the next token.

The producer must make no assumptions about the attributes after the method has been returned: the caller may arbitrarily change it. If the producer needs to preserve the state for subsequent calls, it can use AttributeSource.captureState() to create a copy of the current attribute state.

This method is called for every token of a document, so an efficient implementation is crucial for good performance. To avoid calls to AttributeSource.addAttribute(Class) and AttributeSource.getAttribute(Class), references to all AttributeImpls that this stream uses should be retrieved during instantiation.

To ensure that filters and consumers know which attributes are available, the attributes must be added during instantiation. Filters and consumers are not required to check for availability of attributes in TokenStream.incrementToken().

Specified by:
incrementToken in class TokenStream
Returns:
false for end of stream; true otherwise
Throws:
IOException

reset

public void reset()
           throws IOException
Description copied from class: TokenFilter
Reset the filter as well as the input TokenStream.

Overrides:
reset in class TokenFilter
Throws:
IOException


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