org.apache.lucene.analysis
Class Token

java.lang.Object
  extended by org.apache.lucene.analysis.Token
All Implemented Interfaces:
Cloneable

public class Token
extends Object
implements Cloneable

A Token is an occurence of a term from the text of a field. It consists of a term's text, the start and end offset of the term in the text of the field, and a type string.

The start and end offsets permit applications to re-associate a token with its source text, e.g., to display highlighted query terms in a document browser, or to show matching text fragments in a KWIC (KeyWord In Context) display, etc.

The type is an interned string, assigned by a lexical analyzer (a.k.a. tokenizer), naming the lexical or syntactic class that the token belongs to. For example an end of sentence marker token might be implemented with type "eos". The default token type is "word".

A Token can optionally have metadata (a.k.a. Payload) in the form of a variable length byte array. Use TermPositions.getPayloadLength() and TermPositions.getPayload(byte[], int) to retrieve the payloads from the index.

WARNING: The status of the Payloads feature is experimental. The APIs introduced here might change in the future and will not be supported anymore in such a case.

See Also:
Payload

Constructor Summary
Token(String text, int start, int end)
          Constructs a Token with the given term text, and start & end offsets.
Token(String text, int start, int end, String typ)
          Constructs a Token with the given text, start and end offsets, & type.
 
Method Summary
 Object clone()
           
 int endOffset()
          Returns this Token's ending offset, one greater than the position of the last character corresponding to this token in the source text.
 Payload getPayload()
          Returns this Token's payload.
 int getPositionIncrement()
          Returns the position increment of this Token.
 void setPayload(Payload payload)
          Sets this Token's payload.
 void setPositionIncrement(int positionIncrement)
          Set the position increment.
 void setTermText(String text)
          Sets the Token's term text.
 int startOffset()
          Returns this Token's starting offset, the position of the first character corresponding to this token in the source text.
 String termText()
          Returns the Token's term text.
 String toString()
           
 String type()
          Returns this Token's lexical type.
 
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

Token

public Token(String text,
             int start,
             int end)
Constructs a Token with the given term text, and start & end offsets. The type defaults to "word."


Token

public Token(String text,
             int start,
             int end,
             String typ)
Constructs a Token with the given text, start and end offsets, & type.

Method Detail

setPositionIncrement

public void setPositionIncrement(int positionIncrement)
Set the position increment. This determines the position of this token relative to the previous Token in a TokenStream, used in phrase searching.

The default value is one.

Some common uses for this are:

See Also:
TermPositions

getPositionIncrement

public int getPositionIncrement()
Returns the position increment of this Token.

See Also:
setPositionIncrement(int)

setTermText

public void setTermText(String text)
Sets the Token's term text.


termText

public final String termText()
Returns the Token's term text.


startOffset

public final int startOffset()
Returns this Token's starting offset, the position of the first character corresponding to this token in the source text. Note that the difference between endOffset() and startOffset() may not be equal to termText.length(), as the term text may have been altered by a stemmer or some other filter.


endOffset

public final int endOffset()
Returns this Token's ending offset, one greater than the position of the last character corresponding to this token in the source text.


type

public final String type()
Returns this Token's lexical type. Defaults to "word".


setPayload

public void setPayload(Payload payload)
Sets this Token's payload.

WARNING: The status of the Payloads feature is experimental. The APIs introduced here might change in the future and will not be supported anymore in such a case.


getPayload

public Payload getPayload()
Returns this Token's payload.

WARNING: The status of the Payloads feature is experimental. The APIs introduced here might change in the future and will not be supported anymore in such a case.


toString

public String toString()
Overrides:
toString in class Object

clone

public Object clone()
Overrides:
clone in class Object


Copyright © 2000-2008 Apache Software Foundation. All Rights Reserved.