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/*
* LingPipe v. 4.1.0
* Copyright (C) 2003-2011 Alias-i
*
* This program is licensed under the Alias-i Royalty Free License
* Version 1 WITHOUT ANY WARRANTY, without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the Alias-i
* Royalty Free License Version 1 for more details.
*
* You should have received a copy of the Alias-i Royalty Free License
* Version 1 along with this program; if not, visit
* http://alias-i.com/lingpipe/licenses/lingpipe-license-1.txt or contact
* Alias-i, Inc. at 181 North 11th Street, Suite 401, Brooklyn, NY 11211,
* +1 (718) 290-9170.
*/
package com.aliasi.sentences;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
/**
* An AbstractSentenceModel implements a sentence model
* in terms of the method that adds indices to the collection.
* Subclasses must only implement the method {@link
* #boundaryIndices(String[],String[],int,int,Collection)}, which adds
* an Integer to the collection for each token index
* which is sentence final.
*
* The abstract model also adds
* the method {@link #boundaryIndices(String[],String[],int,int)} for
* operating over slices of parallel arrays of tokens and whitespaces.
*
*
The static utility methods {@link #verifyBounds(String[],String[],int,int)}
* and {@link #verifyTokensWhitespaces(String[],String[])} may be used
* by subclasses to verify that the inputs to the sentence detection
* methods are legal.
*
* @author Bob Carpenter
* @version 3.8
* @since LingPipe1.0
*/
public abstract class AbstractSentenceModel implements SentenceModel {
/**
* Construct an abstract sentence model. Because this class is
* abstract, this constructor may only be called by subclasses.
*/
protected AbstractSentenceModel() {
/* do nothing */
}
/**
* Returns an array of indices of sentence-final tokens.
*
*
If this method is overridden in a subclass, the static
* method {@link #verifyTokensWhitespaces(String[],String[])} should
* be called to verify that the arguments are valid.
*
* @param tokens Array of tokens to annotate.
* @param whitespaces Array of whitespaces to annotate.
* @return Array of integers indicating indices of tokens that
* are sentence final.
* @throws IllegalArgumentException If the array of whitespaces is
* not one element longer than the array of tokens.
*/
public int[] boundaryIndices(String[] tokens, String[] whitespaces) {
verifyTokensWhitespaces(tokens,whitespaces);
return boundaryIndices(tokens,whitespaces,0,tokens.length);
}
/**
* Returns an array of indices of sentence-final tokens
* for the slice of the token and whitespace arrays specified.
*
*
If this method is overridden in a subclass, the static
* method {@link #verifyBounds(String[],String[],int,int)} should
* be called by implementations to verify that the arguments are
* valid.
*
*
* @param tokens Array of tokens to annotate.
* @param whitespaces Array of whitespaces to annotate.
* @param start Index of first token to annotate.
* @param length Number of tokens to annotate.
* @return Array of integers indicating indices of tokens that
* are sentence final.
* @throws IllegalArgumentException If the array of whitespaces is
* not one element longer than the array of tokens.
*/
public int[] boundaryIndices(String[] tokens, String[] whitespaces,
int start, int length) {
verifyBounds(tokens,whitespaces,start,length);
List boundaries = new ArrayList();
boundaryIndices(tokens,whitespaces,start,length,boundaries);
int[] result = new int[boundaries.size()];
for (int i = 0; i < result.length; ++i)
result[i] = boundaries.get(i).intValue();
return result;
}
/**
* Adds the sentence final token indices as Integer
* instances to the specified collection, only considering tokens
* between index start and end-1
* inclusive.
*
* The abstract implementations provide an array list for
* the collection of indices, and results will be returned in
* the order they are added to the collection.
*
*
The static method {@link
* #verifyBounds(String[],String[],int,int)} should be called by
* implementations to verify that the arguments are valid.
*
* @param tokens Array of tokens to annotate.
* @param whitespaces Array of whitespaces to annotate.
* @param start Index of first token to annotate.
* @param length Number of tokens to annotate.
* @param indices Collection into which to write the boundary
* indices.
* @throws IllegalArgumentException If the array of whitespaces
* and tokens is not long enough for the start and length parameters.
*/
public abstract void boundaryIndices(String[] tokens,
String[] whitespaces,
int start, int length,
Collection indices);
/**
* Throws an illegal argument exception if the arrays of tokens is
* not as long as the start plus length, or if the array of
* whitespaces is not at least one element longer than the start
* plus length.
*
* @param tokens Array of tokens to annotate.
* @param whitespaces Array of whitespaces to annotate.
* @param start Index of first token to annotate.
* @param length Number of tokens to annotate.
* @throws IllegalArgumentException If the array of whitespaces
* and tokens is not long enough for the start and length parameters.
*/
protected static void verifyBounds(String[] tokens, String[] whitespaces,
int start, int length) {
if (tokens.length < start+length) {
String msg = "Token array must be at least as long as start+length."
+ " tokens.length=" + tokens.length
+ " start=" + start
+ " length=" + length;
throw new IllegalArgumentException(msg);
}
if (whitespaces.length <= start+length) {
String msg = "Whitespace array must be longer than start+length."
+ " whitespaces.length=" + whitespaces.length
+ " start=" + start
+ " length=" + length;
throw new IllegalArgumentException(msg);
}
}
/**
* Throws an illegal argument exception if the array of whitespaces
* is not one longer than the array of tokens.
*
* @param tokens Array of tokens to annotate.
* @param whitespaces Array of whitespaces to annotate.
* @throws IllegalArgumentException If the array of whitespaces
* is not one longer than the array of tokens.
*/
protected static void verifyTokensWhitespaces(String[] tokens,
String[] whitespaces) {
if (whitespaces.length == tokens.length+1) return;
String msg = "Whitespaces array must be one longer than tokens."
+ " Found tokens.length=" + tokens.length
+ " whitespaces.length=" + whitespaces.length;
throw new IllegalArgumentException(msg);
}
}