TagError.java

package edu.northwestern.at.morphadorner.tools.taggertrainer;

/*	Please see the license information at the end of this file. */

import java.util.*;

import edu.northwestern.at.morphadorner.tools.taggertrainer.*;
import edu.northwestern.at.utils.*;

/**	Tag confusion matrix entry.
 *
 *	<p>
 *	A TagError entry contains a (correct tag, incorrect tag, error count)
 *	tuple.  The error count is the number of times a part of speech
 *	tagger generated "incorrect tag" instead of "correct tag" in
 *	a tagged corpus.  A list of TagError entries can be used by a
 *	transformation based learning program to generate contextual rules
 *	to correct the tag errors.
 *	</p>
 */

public class TagError implements Comparable
{
	/**	Correct tag. */

	public final String correctTag;

	/**	Incorrect tag. */

	public final String incorrectTag;

	/**	List of word positions where this error occurs.
	 */

	public final List<Integer> errorPositions;

	/**	Number of times incorrect tag appears instead of correct tag. */

	public final int incorrectTagCount;

	/**	The hash code. */

	protected final int hashCode;

	/**	Create a tag error entry.
	 *
	 *	@param	correctTag			The correct part of speech tag.
	 *	@param	incorrectTag		The incorrect part of speech tag.
	 *	@param	errorPositions		The list of tag error positions.
	 */

	public TagError
	(
		String correctTag ,
		String incorrectTag ,
		List<Integer> errorPositions
	)
	{
		this.correctTag			= correctTag;
		this.incorrectTag		= incorrectTag;
		this.errorPositions		= errorPositions;
		this.incorrectTagCount	= this.errorPositions.size();

								//	Compute hash code.

		this.hashCode			=
			this.correctTag.hashCode() ^
			this.incorrectTag.hashCode() ^
			(new Integer( incorrectTagCount )).hashCode();
	}

    /**	Check if another object is equal to this one.
   	 *
     *	@param	object  Other object to test for equality.
   	 *
   	 *	@return			true if other object is equal to this one.
   	 */

	public boolean equals( Object object )
	{
		boolean	result	= false;

		if ( ( object != null ) && ( object instanceof TagError ) )
		{
			TagError otherTagError	= (TagError)object;

			result	=
				( correctTag.equals( otherTagError.correctTag ) ) &&
				( incorrectTag.equals( otherTagError.incorrectTag ) ) &&
				( incorrectTagCount == otherTagError.incorrectTagCount );
		}

		return result;
	}

 	/**	Compare this object with another.
 	 *
	 *	@param	object	The other object.
 	 *
	 *	@return			< 0 if the other object is less than this one,
	 *					= 0 if the two objects are equal,
	 *					> 0 if the other object is greater than this one.
 	 *
	 *	<p>
 	 *	We use compareTo on the array entries in the key.
	 *	This may not give the desired result if the array entries
 	 *	are themselves arrays.
 	 *	</p>
	 */

	public int compareTo( Object object )
	{
		int result	= 0;

		if ( ( object == null ) ||
			!( object instanceof TagError ) )
		{
			result	= Integer.MIN_VALUE;
		}
		else
		{
			TagError otherTagError	= (TagError)object;

			if ( incorrectTagCount > otherTagError.incorrectTagCount )
			{
				result	= -1;
			}
			else if ( incorrectTagCount < otherTagError.incorrectTagCount )
			{
				result	= 1;
			}

			if ( result == 0 )
			{
				result	=
					Compare.compare(
						incorrectTag , otherTagError.incorrectTag );
			}

			if ( result == 0 )
			{
				result	=
					Compare.compare(
						correctTag , otherTagError.correctTag );
           	}
		}

		return result;
	}

	/**	Get the hash code of the keys.
	 *
	 *	@return		The hash code.
	 */

	public int hashCode()
	{
		return hashCode;
	}

	/**	Return a string representation of this object.
	 *
	 *	@return		A string representation of this object.
	 */

	public String toString()
	{
		return
			incorrectTagCount + " " +
			incorrectTag + " should be " + correctTag;
	}
}

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