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The Stemmer.java Java example source code
/**
* @test
* @bug 7070134
* @summary Hotspot crashes with sigsegv from PorterStemmer
*
* @run shell Test7070134.sh
*/
/*
Porter stemmer in Java. The original paper is in
Porter, 1980, An algorithm for suffix stripping, Program, Vol. 14,
no. 3, pp 130-137,
http://www.tartarus.org/~martin/PorterStemmer
The software is completely free for any purpose, unless notes at the head
of the program text indicates otherwise (which is rare). In any case,
the notes about licensing are never more restrictive than the BSD License.
In every case where the software is not written by me (Martin Porter),
this licensing arrangement has been endorsed by the contributor, and it is
therefore unnecessary to ask the contributor again to confirm it.
I have not asked any contributors (or their employers, if they have them)
for proofs that they have the right to distribute their software in this way.
History:
Release 1
Bug 1 (reported by Gonzalo Parra 16/10/99) fixed as marked below.
The words 'aed', 'eed', 'oed' leave k at 'a' for step 3, and b[k-1]
is then out outside the bounds of b.
Release 2
Similarly,
Bug 2 (reported by Steve Dyrdahl 22/2/00) fixed as marked below.
'ion' by itself leaves j = -1 in the test for 'ion' in step 5, and
b[j] is then outside the bounds of b.
Release 3
Considerably revised 4/9/00 in the light of many helpful suggestions
from Brian Goetz of Quiotix Corporation (brian@quiotix.com).
Release 4
*/
import java.io.*;
/**
* Stemmer, implementing the Porter Stemming Algorithm
*
* The Stemmer class transforms a word into its root form. The input
* word can be provided a character at time (by calling add()), or at once
* by calling one of the various stem(something) methods.
*/
class Stemmer
{ private char[] b;
private int i, /* offset into b */
i_end, /* offset to end of stemmed word */
j, k;
private static final int INC = 50;
/* unit of size whereby b is increased */
public Stemmer()
{ b = new char[INC];
i = 0;
i_end = 0;
}
/**
* Add a character to the word being stemmed. When you are finished
* adding characters, you can call stem(void) to stem the word.
*/
public void add(char ch)
{ if (i == b.length)
{ char[] new_b = new char[i+INC];
for (int c = 0; c < i; c++) new_b[c] = b[c];
b = new_b;
}
b[i++] = ch;
}
/** Adds wLen characters to the word being stemmed contained in a portion
* of a char[] array. This is like repeated calls of add(char ch), but
* faster.
*/
public void add(char[] w, int wLen)
{ if (i+wLen >= b.length)
{ char[] new_b = new char[i+wLen+INC];
for (int c = 0; c < i; c++) new_b[c] = b[c];
b = new_b;
}
for (int c = 0; c < wLen; c++) b[i++] = w[c];
}
/**
* After a word has been stemmed, it can be retrieved by toString(),
* or a reference to the internal buffer can be retrieved by getResultBuffer
* and getResultLength (which is generally more efficient.)
*/
public String toString() { return new String(b,0,i_end); }
/**
* Returns the length of the word resulting from the stemming process.
*/
public int getResultLength() { return i_end; }
/**
* Returns a reference to a character buffer containing the results of
* the stemming process. You also need to consult getResultLength()
* to determine the length of the result.
*/
public char[] getResultBuffer() { return b; }
/* cons(i) is true <=> b[i] is a consonant. */
private final boolean cons(int i)
{ switch (b[i])
{ case 'a': case 'e': case 'i': case 'o': case 'u': return false;
case 'y': return (i==0) ? true : !cons(i-1);
default: return true;
}
}
/* m() measures the number of consonant sequences between 0 and j. if c is
a consonant sequence and v a vowel sequence, and <..> indicates arbitrary
presence,
<c> gives 0
<c>vc gives 1
<c>vcvc gives 2
<c>vcvcvc gives 3
....
*/
private final int m()
{ int n = 0;
int i = 0;
while(true)
{ if (i > j) return n;
if (! cons(i)) break; i++;
}
i++;
while(true)
{ while(true)
{ if (i > j) return n;
if (cons(i)) break;
i++;
}
i++;
n++;
while(true)
{ if (i > j) return n;
if (! cons(i)) break;
i++;
}
i++;
}
}
/* vowelinstem() is true <=> 0,...j contains a vowel */
private final boolean vowelinstem()
{ int i; for (i = 0; i <= j; i++) if (! cons(i)) return true;
return false;
}
/* doublec(j) is true <=> j,(j-1) contain a double consonant. */
private final boolean doublec(int j)
{ if (j < 1) return false;
if (b[j] != b[j-1]) return false;
return cons(j);
}
/* cvc(i) is true <=> i-2,i-1,i has the form consonant - vowel - consonant
and also if the second c is not w,x or y. this is used when trying to
restore an e at the end of a short word. e.g.
cav(e), lov(e), hop(e), crim(e), but
snow, box, tray.
*/
private final boolean cvc(int i)
{ if (i < 2 || !cons(i) || cons(i-1) || !cons(i-2)) return false;
{ int ch = b[i];
if (ch == 'w' || ch == 'x' || ch == 'y') return false;
}
return true;
}
private final boolean ends(String s)
{ int l = s.length();
int o = k-l+1;
if (o < 0) return false;
for (int i = 0; i < l; i++) if (b[o+i] != s.charAt(i)) return false;
j = k-l;
return true;
}
/* setto(s) sets (j+1),...k to the characters in the string s, readjusting
k. */
private final void setto(String s)
{ int l = s.length();
int o = j+1;
for (int i = 0; i < l; i++) b[o+i] = s.charAt(i);
k = j+l;
}
/* r(s) is used further down. */
private final void r(String s) { if (m() > 0) setto(s); }
/* step1() gets rid of plurals and -ed or -ing. e.g.
caresses -> caress
ponies -> poni
ties -> ti
caress -> caress
cats -> cat
feed -> feed
agreed -> agree
disabled -> disable
matting -> mat
mating -> mate
meeting -> meet
milling -> mill
messing -> mess
meetings -> meet
*/
private final void step1()
{ if (b[k] == 's')
{ if (ends("sses")) k -= 2; else
if (ends("ies")) setto("i"); else
if (b[k-1] != 's') k--;
}
if (ends("eed")) { if (m() > 0) k--; } else
if ((ends("ed") || ends("ing")) && vowelinstem())
{ k = j;
if (ends("at")) setto("ate"); else
if (ends("bl")) setto("ble"); else
if (ends("iz")) setto("ize"); else
if (doublec(k))
{ k--;
{ int ch = b[k];
if (ch == 'l' || ch == 's' || ch == 'z') k++;
}
}
else if (m() == 1 && cvc(k)) setto("e");
}
}
/* step2() turns terminal y to i when there is another vowel in the stem. */
private final void step2() { if (ends("y") && vowelinstem()) b[k] = 'i'; }
/* step3() maps double suffices to single ones. so -ization ( = -ize plus
-ation) maps to -ize etc. note that the string before the suffix must give
m() > 0. */
private final void step3() { if (k == 0) return; /* For Bug 1 */ switch (b[k-1])
{
case 'a': if (ends("ational")) { r("ate"); break; }
if (ends("tional")) { r("tion"); break; }
break;
case 'c': if (ends("enci")) { r("ence"); break; }
if (ends("anci")) { r("ance"); break; }
break;
case 'e': if (ends("izer")) { r("ize"); break; }
break;
case 'l': if (ends("bli")) { r("ble"); break; }
if (ends("alli")) { r("al"); break; }
if (ends("entli")) { r("ent"); break; }
if (ends("eli")) { r("e"); break; }
if (ends("ousli")) { r("ous"); break; }
break;
case 'o': if (ends("ization")) { r("ize"); break; }
if (ends("ation")) { r("ate"); break; }
if (ends("ator")) { r("ate"); break; }
break;
case 's': if (ends("alism")) { r("al"); break; }
if (ends("iveness")) { r("ive"); break; }
if (ends("fulness")) { r("ful"); break; }
if (ends("ousness")) { r("ous"); break; }
break;
case 't': if (ends("aliti")) { r("al"); break; }
if (ends("iviti")) { r("ive"); break; }
if (ends("biliti")) { r("ble"); break; }
break;
case 'g': if (ends("logi")) { r("log"); break; }
} }
/* step4() deals with -ic-, -full, -ness etc. similar strategy to step3. */
private final void step4() { switch (b[k])
{
case 'e': if (ends("icate")) { r("ic"); break; }
if (ends("ative")) { r(""); break; }
if (ends("alize")) { r("al"); break; }
break;
case 'i': if (ends("iciti")) { r("ic"); break; }
break;
case 'l': if (ends("ical")) { r("ic"); break; }
if (ends("ful")) { r(""); break; }
break;
case 's': if (ends("ness")) { r(""); break; }
break;
} }
/* step5() takes off -ant, -ence etc., in context <c>vcvc. */
private final void step5()
{ if (k == 0) return; /* for Bug 1 */ switch (b[k-1])
{ case 'a': if (ends("al")) break; return;
case 'c': if (ends("ance")) break;
if (ends("ence")) break; return;
case 'e': if (ends("er")) break; return;
case 'i': if (ends("ic")) break; return;
case 'l': if (ends("able")) break;
if (ends("ible")) break; return;
case 'n': if (ends("ant")) break;
if (ends("ement")) break;
if (ends("ment")) break;
/* element etc. not stripped before the m */
if (ends("ent")) break; return;
case 'o': if (ends("ion") && j >= 0 && (b[j] == 's' || b[j] == 't')) break;
/* j >= 0 fixes Bug 2 */
if (ends("ou")) break; return;
/* takes care of -ous */
case 's': if (ends("ism")) break; return;
case 't': if (ends("ate")) break;
if (ends("iti")) break; return;
case 'u': if (ends("ous")) break; return;
case 'v': if (ends("ive")) break; return;
case 'z': if (ends("ize")) break; return;
default: return;
}
if (m() > 1) k = j;
}
/* step6() removes a final -e if m() > 1. */
private final void step6()
{ j = k;
if (b[k] == 'e')
{ int a = m();
if (a > 1 || a == 1 && !cvc(k-1)) k--;
}
if (b[k] == 'l' && doublec(k) && m() > 1) k--;
}
/** Stem the word placed into the Stemmer buffer through calls to add().
* Returns true if the stemming process resulted in a word different
* from the input. You can retrieve the result with
* getResultLength()/getResultBuffer() or toString().
*/
public void stem()
{ k = i - 1;
if (k > 1) { step1(); step2(); step3(); step4(); step5(); step6(); }
i_end = k+1; i = 0;
}
/** Test program for demonstrating the Stemmer. It reads text from a
* a list of files, stems each word, and writes the result to standard
* output. Note that the word stemmed is expected to be in lower case:
* forcing lower case must be done outside the Stemmer class.
* Usage: Stemmer file-name file-name ...
*/
public static void main(String[] args)
{
char[] w = new char[501];
Stemmer s = new Stemmer();
for (int i = 0; i < args.length; i++)
try
{
FileInputStream in = new FileInputStream(args[i]);
try
{ while(true)
{ int ch = in.read();
if (Character.isLetter((char) ch))
{
int j = 0;
while(true)
{ ch = Character.toLowerCase((char) ch);
w[j] = (char) ch;
if (j < 500) j++;
ch = in.read();
if (!Character.isLetter((char) ch))
{
/* to test add(char ch) */
for (int c = 0; c < j; c++) s.add(w[c]);
/* or, to test add(char[] w, int j) */
/* s.add(w, j); */
s.stem();
{ String u;
/* and now, to test toString() : */
u = s.toString();
/* to test getResultBuffer(), getResultLength() : */
/* u = new String(s.getResultBuffer(), 0, s.getResultLength()); */
System.out.print(u);
}
break;
}
}
}
if (ch < 0) break;
System.out.print((char)ch);
}
}
catch (IOException e)
{ System.out.println("error reading " + args[i]);
break;
}
}
catch (FileNotFoundException e)
{ System.out.println("file " + args[i] + " not found");
break;
}
}
}
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