org.terrier.utility

Class StringComparator

java.lang.Object

org.terrier.utility.StringComparator

All Implemented Interfaces:

Comparator<String>

public class StringComparator
extends Object
implements Comparator<String>

Compares two strings which may have fixed length fields separated with a non word character (eg a dash), and a last field which corresponds to an integer. Two examples of such strings are XXX-XXX-012389 and XXX-XXX-1242 (XXX-XXX-1242 < XXX-XXX-012389 when compared using this comparator.

This class is primarily used for comparing docnos, especially for TREC like collections. The docnos in the DocumentIndex as expected to be sorted in an order compatible with this comparator.

Sorting Algorithm:

• Split strings on non word characters
• For each field, left-most first:
• Compare as number if both field contains only numbers, return if not equal
• Compare as string if both fields do not contain only numbers, return if not equal

Author:

Vassilis Plachouras, Craig Macdonald

Field Summary

Fields

Modifier and Type	Field and Description
static StringComparator	Me An instantiation of this class.

Constructor Summary

Constructors

Constructor and Description
StringComparator()

Method Summary

Modifier and Type	Method and Description
int	compare(String s1, String s2) Compares two Strings, which have a number of fields that are separated by one or more non-alphanumeric characters.
static int	compareObjects(Object o1, Object o2) A static access method, to prevent having to instantiate a comparator This has the same parameters, return and implementation as compare(Object,Object)
static int	compareStrings(String s1, String s2) A static access method, to prevent having to instantiate a comparator This has the same parameters, return and implementation as compare(Object,Object)
static void	main(String[] args) Will display the comparator value between two strings from the command line arguments.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Comparator

comparing, comparing, comparingDouble, comparingInt, comparingLong, equals, naturalOrder, nullsFirst, nullsLast, reversed, reverseOrder, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

Field Detail

Me

public static final StringComparator Me

An instantiation of this class.

Constructor Detail

StringComparator

public StringComparator()

Method Detail

compare

public int compare(String s1,
                   String s2)

Compares two Strings, which have a number of fields that are separated by one or more non-alphanumeric characters.

Specified by:

compare in interface Comparator<String>

Parameters:

s1 - the first string object to compare.

s2 - the second string object to compare.

Returns:

int -1, zero, or 1 if the first argument is less than, equal to, or greater than the second argument, respectively.

compareObjects

public static int compareObjects(Object o1,
                                 Object o2)

A static access method, to prevent having to instantiate a comparator This has the same parameters, return and implementation as compare(Object,Object)

Since:

1.1.0

compareStrings

public static int compareStrings(String s1,
                                 String s2)

A static access method, to prevent having to instantiate a comparator This has the same parameters, return and implementation as compare(Object,Object)

Since:

1.1.0

main

public static void main(String[] args)

Will display the comparator value between two strings from the command line arguments.