Token (Lucene 2.4.0 API)

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org.apache.lucene.analysis
Class Token

java.lang.Object
  org.apache.lucene.analysis.Token

All Implemented Interfaces:: Cloneable

public class Token
extends Object
implements Cloneable
extends Object
implements Cloneable

A Token is an occurrence 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 a 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.

NOTE: As of 2.3, Token stores the term text internally as a malleable char[] termBuffer instead of String termText. The indexing code and core tokenizers have been changed to re-use a single Token instance, changing its buffer and other fields in-place as the Token is processed. This provides substantially better indexing performance as it saves the GC cost of new'ing a Token and String for every term. The APIs that accept String termText are still available but a warning about the associated performance cost has been added (below). The termText() method has been deprecated.

Tokenizers and filters should try to re-use a Token instance when possible for best performance, by implementing the TokenStream.next(Token) API. Failing that, to create a new Token you should first use one of the constructors that starts with null text. To load the token from a char[] use setTermBuffer(char[], int, int). To load from a String use setTermBuffer(String) or setTermBuffer(String, int, int). Alternatively you can get the Token's termBuffer by calling either termBuffer(), if you know that your text is shorter than the capacity of the termBuffer or resizeTermBuffer(int), if there is any possibility that you may need to grow the buffer. Fill in the characters of your term into this buffer, with String.getChars(int, int, char[], int) if loading from a string, or with System.arraycopy(Object, int, Object, int, int), and finally call setTermLength(int) to set the length of the term text. See LUCENE-969 for details.

Typical reuse patterns:

Copying text from a string (type is reset to #DEFAULT_TYPE if not specified):

    return reusableToken.reinit(string, startOffset, endOffset[, type]);

Copying some text from a string (type is reset to #DEFAULT_TYPE if not specified):

    return reusableToken.reinit(string, 0, string.length(), startOffset, endOffset[, type]);

Copying text from char[] buffer (type is reset to #DEFAULT_TYPE if not specified):

    return reusableToken.reinit(buffer, 0, buffer.length, startOffset, endOffset[, type]);

Copying some text from a char[] buffer (type is reset to #DEFAULT_TYPE if not specified):

    return reusableToken.reinit(buffer, start, end - start, startOffset, endOffset[, type]);

Copying from one one Token to another (type is reset to #DEFAULT_TYPE if not specified):

    return reusableToken.reinit(source.termBuffer(), 0, source.termLength(), source.startOffset(), source.endOffset()[, source.type()]);

A few things to note:

clear() initializes most of the fields to default values, but not startOffset, endOffset and type.
Because TokenStreams can be chained, one cannot assume that the Token's current type is correct.
The startOffset and endOffset represent the start and offset in the source text. So be careful in adjusting them.
When caching a reusable token, clone it. When injecting a cached token into a stream that can be reset, clone it again.

See Also:: Payload

Field Summary
`static String`	`DEFAULT_TYPE`

Constructor Summary
`Token()` Constructs a Token will null text.
`Token(char[] startTermBuffer, int termBufferOffset, int termBufferLength, int start, int end)` Constructs a Token with the given term buffer (offset & length), start and end offsets
`Token(int start, int end)` Constructs a Token with null text and start & end offsets.
`Token(int start, int end, int flags)` Constructs a Token with null text and start & end offsets plus flags.
`Token(int start, int end, String typ)` Constructs a Token with null text and start & end offsets plus the Token type.
`Token(String text, int start, int end)` Deprecated.
`Token(String text, int start, int end, int flags)` Deprecated.
`Token(String text, int start, int end, String typ)` Deprecated.

Method Summary
`void`	`clear()` Resets the term text, payload, flags, and positionIncrement to default.
`Object`	`clone()`
`Token`	`clone(char[] newTermBuffer, int newTermOffset, int newTermLength, int newStartOffset, int newEndOffset)` Makes a clone, but replaces the term buffer & start/end offset in the process.
`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.
`boolean`	`equals(Object obj)`
`int`	`getFlags()` EXPERIMENTAL: While we think this is here to stay, we may want to change it to be a long.
`Payload`	`getPayload()` Returns this Token's payload.
`int`	`getPositionIncrement()` Returns the position increment of this Token.
`int`	`hashCode()`
`Token`	`reinit(char[] newTermBuffer, int newTermOffset, int newTermLength, int newStartOffset, int newEndOffset)` Shorthand for calling `clear()`, `setTermBuffer(char[], int, int)`, `setStartOffset(int)`, `setEndOffset(int)` `setType(java.lang.String)` on Token.DEFAULT_TYPE
`Token`	`reinit(char[] newTermBuffer, int newTermOffset, int newTermLength, int newStartOffset, int newEndOffset, String newType)` Shorthand for calling `clear()`, `setTermBuffer(char[], int, int)`, `setStartOffset(int)`, `setEndOffset(int)`, `setType(java.lang.String)`
`Token`	`reinit(String newTerm, int newStartOffset, int newEndOffset)` Shorthand for calling `clear()`, `setTermBuffer(String)`, `setStartOffset(int)`, `setEndOffset(int)` `setType(java.lang.String)` on Token.DEFAULT_TYPE
`Token`	`reinit(String newTerm, int newTermOffset, int newTermLength, int newStartOffset, int newEndOffset)` Shorthand for calling `clear()`, `setTermBuffer(String, int, int)`, `setStartOffset(int)`, `setEndOffset(int)` `setType(java.lang.String)` on Token.DEFAULT_TYPE
`Token`	`reinit(String newTerm, int newTermOffset, int newTermLength, int newStartOffset, int newEndOffset, String newType)` Shorthand for calling `clear()`, `setTermBuffer(String, int, int)`, `setStartOffset(int)`, `setEndOffset(int)` `setType(java.lang.String)`
`Token`	`reinit(String newTerm, int newStartOffset, int newEndOffset, String newType)` Shorthand for calling `clear()`, `setTermBuffer(String)`, `setStartOffset(int)`, `setEndOffset(int)` `setType(java.lang.String)`
`void`	`reinit(Token prototype)` Copy the prototype token's fields into this one.
`void`	`reinit(Token prototype, char[] newTermBuffer, int offset, int length)` Copy the prototype token's fields into this one, with a different term.
`void`	`reinit(Token prototype, String newTerm)` Copy the prototype token's fields into this one, with a different term.
`char[]`	`resizeTermBuffer(int newSize)` Grows the termBuffer to at least size newSize, preserving the existing content.
`void`	`setEndOffset(int offset)` Set the ending offset.
`void`	`setFlags(int flags)`
`void`	`setPayload(Payload payload)` Sets this Token's payload.
`void`	`setPositionIncrement(int positionIncrement)` Set the position increment.
`void`	`setStartOffset(int offset)` Set the starting offset.
`void`	`setTermBuffer(char[] buffer, int offset, int length)` Copies the contents of buffer, starting at offset for length characters, into the termBuffer array.
`void`	`setTermBuffer(String buffer)` Copies the contents of buffer into the termBuffer array.
`void`	`setTermBuffer(String buffer, int offset, int length)` Copies the contents of buffer, starting at offset and continuing for length characters, into the termBuffer array.
`void`	`setTermLength(int length)` Set number of valid characters (length of the term) in the termBuffer array.
`void`	`setTermText(String text)` Deprecated. use `setTermBuffer(char[], int, int)` or `setTermBuffer(String)` or `setTermBuffer(String, int, int)`.
`void`	`setType(String type)` Set the lexical type.
`int`	`startOffset()` Returns this Token's starting offset, the position of the first character corresponding to this token in the source text.
`String`	`term()` Returns the Token's term text.
`char[]`	`termBuffer()` Returns the internal termBuffer character array which you can then directly alter.
`int`	`termLength()` Return number of valid characters (length of the term) in the termBuffer array.
`String`	`termText()` Deprecated. This method now has a performance penalty because the text is stored internally in a char[]. If possible, use `termBuffer()` and `termLength()` directly instead. If you really need a String, use `term()`
`String`	`toString()`
`String`	`type()` Returns this Token's lexical type.

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

Field Detail

DEFAULT_TYPE

public static final String DEFAULT_TYPE

See Also:: Constant Field Values

Constructor Detail

Token

public Token()

Constructs a Token will null text.

Token

public Token(int start,
             int end)

Constructs a Token with null text and start & end offsets.

Parameters:: start - start offset in the source text; end - end offset in the source text

Token

public Token(int start,
             int end,
             String typ)

Constructs a Token with null text and start & end offsets plus the Token type.

Parameters:: start - start offset in the source text; end - end offset in the source text; typ - the lexical type of this Token

Token

public Token(int start,
             int end,
             int flags)

Constructs a Token with null text and start & end offsets plus flags. NOTE: flags is EXPERIMENTAL.

Parameters:: start - start offset in the source text; end - end offset in the source text; flags - The bits to set for this token

Token

public Token(String text,
             int start,
             int end)

Deprecated.

Constructs a Token with the given term text, and start & end offsets. The type defaults to "word." NOTE: for better indexing speed you should instead use the char[] termBuffer methods to set the term text.

Parameters:: text - term text; start - start offset; end - end offset

Token

public Token(String text,
             int start,
             int end,
             String typ)

Deprecated.

Constructs a Token with the given text, start and end offsets, & type. NOTE: for better indexing speed you should instead use the char[] termBuffer methods to set the term text.

Parameters:: text - term text; start - start offset; end - end offset; typ - token type

Token

public Token(String text,
             int start,
             int end,
             int flags)

Deprecated.

Constructs a Token with the given text, start and end offsets, & type. NOTE: for better indexing speed you should instead use the char[] termBuffer methods to set the term text.

Parameters:: text -; start -; end -; flags - token type bits

Token

public Token(char[] startTermBuffer,
             int termBufferOffset,
             int termBufferLength,
             int start,
             int end)

Constructs a Token with the given term buffer (offset & length), start and end offsets

Parameters:: startTermBuffer -; termBufferOffset -; termBufferLength -; start -; end -

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:

Set it to zero to put multiple terms in the same position. This is useful if, e.g., a word has multiple stems. Searches for phrases including either stem will match. In this case, all but the first stem's increment should be set to zero: the increment of the first instance should be one. Repeating a token with an increment of zero can also be used to boost the scores of matches on that token.
Set it to values greater than one to inhibit exact phrase matches. If, for example, one does not want phrases to match across removed stop words, then one could build a stop word filter that removes stop words and also sets the increment to the number of stop words removed before each non-stop word. Then exact phrase queries will only match when the terms occur with no intervening stop words.

Parameters:: positionIncrement - the distance from the prior term
See Also:: TermPositions

getPositionIncrement

public int getPositionIncrement()

Returns the position increment of this Token.

See Also:: setPositionIncrement(int)

setTermText

public void setTermText(String text)

Deprecated. use setTermBuffer(char[], int, int) or setTermBuffer(String) or setTermBuffer(String, int, int).

Sets the Token's term text. NOTE: for better indexing speed you should instead use the char[] termBuffer methods to set the term text.

termText

public final String termText()

Deprecated. This method now has a performance penalty because the text is stored internally in a char[]. If possible, use termBuffer() and termLength() directly instead. If you really need a String, use term()

Returns the Token's term text.

term

public final String term()

Returns the Token's term text. This method has a performance penalty because the text is stored internally in a char[]. If possible, use termBuffer() and termLength() directly instead. If you really need a String, use this method, which is nothing more than a convenience call to new String(token.termBuffer(), 0, token.termLength())

setTermBuffer

public final void setTermBuffer(char[] buffer,
                                int offset,
                                int length)

Copies the contents of buffer, starting at offset for length characters, into the termBuffer array.

Parameters:: buffer - the buffer to copy; offset - the index in the buffer of the first character to copy; length - the number of characters to copy

setTermBuffer

public final void setTermBuffer(String buffer)

Copies the contents of buffer into the termBuffer array.

Parameters:: buffer - the buffer to copy

setTermBuffer

public final void setTermBuffer(String buffer,
                                int offset,
                                int length)

Copies the contents of buffer, starting at offset and continuing for length characters, into the termBuffer array.

Parameters:: buffer - the buffer to copy; offset - the index in the buffer of the first character to copy; length - the number of characters to copy

termBuffer

public final char[] termBuffer()

Returns the internal termBuffer character array which you can then directly alter. If the array is too small for your token, use resizeTermBuffer(int) to increase it. After altering the buffer be sure to call setTermLength(int) to record the number of valid characters that were placed into the termBuffer.

resizeTermBuffer

public char[] resizeTermBuffer(int newSize)

Grows the termBuffer to at least size newSize, preserving the existing content. Note: If the next operation is to change the contents of the term buffer use setTermBuffer(char[], int, int), setTermBuffer(String), or setTermBuffer(String, int, int) to optimally combine the resize with the setting of the termBuffer.

Parameters:: newSize - minimum size of the new termBuffer
Returns:: newly created termBuffer with length >= newSize

termLength

public final int termLength()

Return number of valid characters (length of the term) in the termBuffer array.

setTermLength

public final void setTermLength(int length)

Set number of valid characters (length of the term) in the termBuffer array. Use this to truncate the termBuffer or to synchronize with external manipulation of the termBuffer. Note: to grow the size of the array, use resizeTermBuffer(int) first.

Parameters:: length - the truncated length

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.

setStartOffset

public void setStartOffset(int offset)

Set the starting offset.

See Also:: startOffset()

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. The length of the token in the source text is (endOffset - startOffset).

setEndOffset

public void setEndOffset(int offset)

Set the ending offset.

See Also:: endOffset()

type

public final String type()

Returns this Token's lexical type. Defaults to "word".

setType

public final void setType(String type)

Set the lexical type.

See Also:: type()

getFlags

public int getFlags()

EXPERIMENTAL: While we think this is here to stay, we may want to change it to be a long.

Get the bitset for any bits that have been set. This is completely distinct from type(), although they do share similar purposes. The flags can be used to encode information about the token for use by other TokenFilters.

Returns:: The bits

setFlags

public void setFlags(int flags)

See Also:: getFlags()

getPayload

public Payload getPayload()

Returns this Token's payload.

setPayload

public void setPayload(Payload payload)

Sets this Token's payload.

toString

public String toString()

Overrides:: toString in class Object

clear

public void clear()

Resets the term text, payload, flags, and positionIncrement to default. Other fields such as startOffset, endOffset and the token type are not reset since they are normally overwritten by the tokenizer.

clone

public Object clone()

Overrides:: clone in class Object

clone

public Token clone(char[] newTermBuffer,
                   int newTermOffset,
                   int newTermLength,
                   int newStartOffset,
                   int newEndOffset)

Makes a clone, but replaces the term buffer & start/end offset in the process. This is more efficient than doing a full clone (and then calling setTermBuffer) because it saves a wasted copy of the old termBuffer.

equals

public boolean equals(Object obj)

Overrides:: equals in class Object

hashCode

public int hashCode()

Overrides:: hashCode in class Object

reinit

public Token reinit(char[] newTermBuffer,
                    int newTermOffset,
                    int newTermLength,
                    int newStartOffset,
                    int newEndOffset,
                    String newType)

Shorthand for calling clear(), setTermBuffer(char[], int, int), setStartOffset(int), setEndOffset(int), setType(java.lang.String)

Returns:: this Token instance

reinit

public Token reinit(char[] newTermBuffer,
                    int newTermOffset,
                    int newTermLength,
                    int newStartOffset,
                    int newEndOffset)

Shorthand for calling clear(), setTermBuffer(char[], int, int), setStartOffset(int), setEndOffset(int) setType(java.lang.String) on Token.DEFAULT_TYPE

Returns:: this Token instance

reinit

public Token reinit(String newTerm,
                    int newStartOffset,
                    int newEndOffset,
                    String newType)

Shorthand for calling clear(), setTermBuffer(String), setStartOffset(int), setEndOffset(int) setType(java.lang.String)

Returns:: this Token instance

reinit

public Token reinit(String newTerm,
                    int newTermOffset,
                    int newTermLength,
                    int newStartOffset,
                    int newEndOffset,
                    String newType)

Shorthand for calling clear(), setTermBuffer(String, int, int), setStartOffset(int), setEndOffset(int) setType(java.lang.String)

Returns:: this Token instance

reinit

public Token reinit(String newTerm,
                    int newStartOffset,
                    int newEndOffset)

Shorthand for calling clear(), setTermBuffer(String), setStartOffset(int), setEndOffset(int) setType(java.lang.String) on Token.DEFAULT_TYPE

Returns:: this Token instance

reinit

public Token reinit(String newTerm,
                    int newTermOffset,
                    int newTermLength,
                    int newStartOffset,
                    int newEndOffset)

Shorthand for calling clear(), setTermBuffer(String, int, int), setStartOffset(int), setEndOffset(int) setType(java.lang.String) on Token.DEFAULT_TYPE

Returns:: this Token instance

reinit

public void reinit(Token prototype)

Copy the prototype token's fields into this one. Note: Payloads are shared.

Parameters:: prototype -

reinit

public void reinit(Token prototype,
                   String newTerm)

Copy the prototype token's fields into this one, with a different term. Note: Payloads are shared.

Parameters:: prototype -; newTerm -

reinit

public void reinit(Token prototype,
                   char[] newTermBuffer,
                   int offset,
                   int length)

Copy the prototype token's fields into this one, with a different term. Note: Payloads are shared.

Parameters:: prototype -; newTermBuffer -; offset -; length -

Overview

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org.apache.lucene.analysis Class Token

DEFAULT_TYPE

Token

Token

Token

Token

Token

Token

Token

Token

setPositionIncrement

getPositionIncrement

setTermText

termText

term

setTermBuffer

setTermBuffer

setTermBuffer

termBuffer

resizeTermBuffer

termLength

setTermLength

startOffset

setStartOffset

endOffset

setEndOffset

type

setType

getFlags

setFlags

getPayload

setPayload

toString

clear

clone

clone

equals

hashCode

reinit

reinit

reinit

reinit

reinit

reinit

reinit

reinit

reinit

org.apache.lucene.analysis
Class Token