I am kinda new to java. I am taking a course in NLP. I wanna know how I can run an input file on the porter stemmer java code.
Answer
The class below is named PorterAlgo and has various functions for stemming.
package com.mycompany.algo;
class NewString {
public String str;
NewString() {
str = "";
}
}
public class PorterAlgo {
String Clean( String str ) {
int last = str.length();
new Character( str.charAt(0) );
String temp = "";
for ( int i=0; i < last; i++ ) {
if ( Character.isLetterOrDigit( str.charAt(i) ) )
temp += str.charAt(i);
}
return temp;
} //clean
boolean hasSuffix( String word, String suffix, NewString stem ) {
String tmp = "";
if ( word.length() <= suffix.length() )
return false;
if (suffix.length() > 1)
if ( word.charAt( word.length()-2 ) != suffix.charAt( suffix.length()-2 ) )
return false;
stem.str = "";
for ( int i=0; i<word.length()-suffix.length(); i++ )
stem.str += word.charAt( i );
tmp = stem.str;
for ( int i=0; i<suffix.length(); i++ )
tmp += suffix.charAt( i );
if ( tmp.compareTo( word ) == 0 )
return true;
else
return false;
}
boolean vowel( char ch, char prev ) {
switch ( ch ) {
case 'a': case 'e': case 'i': case 'o': case 'u':
return true;
case 'y': {
switch ( prev ) {
case 'a': case 'e': case 'i': case 'o': case 'u':
return false;
default:
return true;
}
}
default :
return false;
}
}
int measure( String stem ) {
int i=0, count = 0;
int length = stem.length();
while ( i < length ) {
for ( ; i < length ; i++ ) {
if ( i > 0 ) {
if ( vowel(stem.charAt(i),stem.charAt(i-1)) )
break;
}
else {
if ( vowel(stem.charAt(i),'a') )
break;
}
}
for ( i++ ; i < length ; i++ ) {
if ( i > 0 ) {
if ( !vowel(stem.charAt(i),stem.charAt(i-1)) )
break;
}
else {
if ( !vowel(stem.charAt(i),'?') )
break;
}
}
if ( i < length ) {
count++;
i++;
}
} //while
return(count);
}
boolean containsVowel( String word ) {
for (int i=0 ; i < word.length(); i++ )
if ( i > 0 ) {
if ( vowel(word.charAt(i),word.charAt(i-1)) )
return true;
}
else {
if ( vowel(word.charAt(0),'a') )
return true;
}
return false;
}
boolean cvc( String str ) {
int length=str.length();
if ( length < 3 )
return false;
if ( (!vowel(str.charAt(length-1),str.charAt(length-2)) )
&& (str.charAt(length-1) != 'w') && (str.charAt(length-1) != 'x') && (str.charAt(length-1) != 'y')
&& (vowel(str.charAt(length-2),str.charAt(length-3))) ) {
if (length == 3) {
if (!vowel(str.charAt(0),'?'))
return true;
else
return false;
}
else {
if (!vowel(str.charAt(length-3),str.charAt(length-4)) )
return true;
else
return false;
}
}
return false;
}
String step1( String str ) {
NewString stem = new NewString();
if ( str.charAt( str.length()-1 ) == 's' ) {
if ( (hasSuffix( str, "sses", stem )) || (hasSuffix( str, "ies", stem)) ){
String tmp = "";
for (int i=0; i<str.length()-2; i++)
tmp += str.charAt(i);
str = tmp;
}
else {
if ( ( str.length() == 1 ) && ( str.charAt(str.length()-1) == 's' ) ) {
str = "";
return str;
}
if ( str.charAt( str.length()-2 ) != 's' ) {
String tmp = "";
for (int i=0; i<str.length()-1; i++)
tmp += str.charAt(i);
str = tmp;
}
}
}
if ( hasSuffix( str,"eed",stem ) ) {
if ( measure( stem.str ) > 0 ) {
String tmp = "";
for (int i=0; i<str.length()-1; i++)
tmp += str.charAt( i );
str = tmp;
}
}
else {
if ( (hasSuffix( str,"ed",stem )) || (hasSuffix( str,"ing",stem )) ) {
if (containsVowel( stem.str )) {
String tmp = "";
for ( int i = 0; i < stem.str.length(); i++)
tmp += str.charAt( i );
str = tmp;
if ( str.length() == 1 )
return str;
if ( ( hasSuffix( str,"at",stem) ) || ( hasSuffix( str,"bl",stem ) ) || ( hasSuffix( str,"iz",stem) ) ) {
str += "e";
}
else {
int length = str.length();
if ( (str.charAt(length-1) == str.charAt(length-2))
&& (str.charAt(length-1) != 'l') && (str.charAt(length-1) != 's') && (str.charAt(length-1) != 'z') ) {
tmp = "";
for (int i=0; i<str.length()-1; i++)
tmp += str.charAt(i);
str = tmp;
}
else
if ( measure( str ) == 1 ) {
if ( cvc(str) )
str += "e";
}
}
}
}
}
if ( hasSuffix(str,"y",stem) )
if ( containsVowel( stem.str ) ) {
String tmp = "";
for (int i=0; i<str.length()-1; i++ )
tmp += str.charAt(i);
str = tmp + "i";
}
return str;
}
String step2( String str ) {
String[][] suffixes = { { "ational", "ate" },
{ "tional", "tion" },
{ "enci", "ence" },
{ "anci", "ance" },
{ "izer", "ize" },
{ "iser", "ize" },
{ "abli", "able" },
{ "alli", "al" },
{ "entli", "ent" },
{ "eli", "e" },
{ "ousli", "ous" },
{ "ization", "ize" },
{ "isation", "ize" },
{ "ation", "ate" },
{ "ator", "ate" },
{ "alism", "al" },
{ "iveness", "ive" },
{ "fulness", "ful" },
{ "ousness", "ous" },
{ "aliti", "al" },
{ "iviti", "ive" },
{ "biliti", "ble" }};
NewString stem = new NewString();
for ( int index = 0 ; index < suffixes.length; index++ ) {
if ( hasSuffix ( str, suffixes[index][0], stem ) ) {
if ( measure ( stem.str ) > 0 ) {
str = stem.str + suffixes[index][1];
return str;
}
}
}
return str;
}
String step3( String str ) {
String[][] suffixes = { { "icate", "ic" },
{ "ative", "" },
{ "alize", "al" },
{ "alise", "al" },
{ "iciti", "ic" },
{ "ical", "ic" },
{ "ful", "" },
{ "ness", "" }};
NewString stem = new NewString();
for ( int index = 0 ; index<suffixes.length; index++ ) {
if ( hasSuffix ( str, suffixes[index][0], stem ))
if ( measure ( stem.str ) > 0 ) {
str = stem.str + suffixes[index][1];
return str;
}
}
return str;
}
String step4( String str ) {
String[] suffixes = { "al", "ance", "ence", "er", "ic", "able", "ible", "ant", "ement", "ment", "ent", "sion", "tion",
"ou", "ism", "ate", "iti", "ous", "ive", "ize", "ise"};
NewString stem = new NewString();
for ( int index = 0 ; index<suffixes.length; index++ ) {
if ( hasSuffix ( str, suffixes[index], stem ) ) {
if ( measure ( stem.str ) > 1 ) {
str = stem.str;
return str;
}
}
}
return str;
}
String step5( String str ) {
if ( str.charAt(str.length()-1) == 'e' ) {
if ( measure(str) > 1 ) {/* measure(str)==measure(stem) if ends in vowel */
String tmp = "";
for ( int i=0; i<str.length()-1; i++ )
tmp += str.charAt( i );
str = tmp;
}
else
if ( measure(str) == 1 ) {
String stem = "";
for ( int i=0; i<str.length()-1; i++ )
stem += str.charAt( i );
if ( !cvc(stem) )
str = stem;
}
}
if ( str.length() == 1 )
return str;
if ( (str.charAt(str.length()-1) == 'l') && (str.charAt(str.length()-2) == 'l') && (measure(str) > 1) )
if ( measure(str) > 1 ) {/* measure(str)==measure(stem) if ends in vowel */
String tmp = "";
for ( int i=0; i<str.length()-1; i++ )
tmp += str.charAt( i );
str = tmp;
}
return str;
}
String stripPrefixes ( String str) {
String[] prefixes = { "kilo", "micro", "milli", "intra", "ultra", "mega", "nano", "pico", "pseudo"};
int last = prefixes.length;
for ( int i=0 ; i<last; i++ ) {
if ( str.startsWith( prefixes[i] ) ) {
String temp = "";
for ( int j=0 ; j< str.length()-prefixes[i].length(); j++ )
temp += str.charAt( j+prefixes[i].length() );
return temp;
}
}
return str;
}
private String stripSuffixes( String str ) {
str = step1( str );
if ( str.length() >= 1 )
str = step2( str );
if ( str.length() >= 1 )
str = step3( str );
if ( str.length() >= 1 )
str = step4( str );
if ( str.length() >= 1 )
str = step5( str );
return str;
}
public String stripAffixes( String str ) {
str = str.toLowerCase();
str = Clean(str);
if (( str != "" ) && (str.length() > 2)) {
str = stripPrefixes(str);
if (str != "" )
str = stripSuffixes(str);
}
return str;
} //stripAffixes
} //class
Given below is a class PorterCheck.java
package com.mycompany.algo;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.*;
public class PorterCheck {
private static final String DEFAULT_TEST_FILE = "C:/Users/vaibhav/Desktop/rev.txt";
public static void main(String args[]) throws IOException{
PorterAlgo pa = new PorterAlgo();
//checks for vowels in a given string
System.out.println(pa.containsVowel("vaibhav"));
//removes special characters
System.out.println(pa.Clean("vaibhav's book"));
//check for a given suffix
NewString stem = new NewString();
System.out.println(pa.hasSuffix("corresponding","ing",stem));
//stemming the words
ArrayList<String> tok = new ArrayList<String>();
String[] tokens = {"normalize","technical","education"};
for (String x: tokens){
tok.add(x);
}
System.out.println(completeStem(tok));
String fileName = ((args.length > 0) ? args[0] : DEFAULT_TEST_FILE);
FileReader fileReader = new FileReader(new File(fileName));
FileTokenizer fileTokenizer = new FileTokenizer();
List<String> tokens1 = fileTokenizer.tokenize(fileReader);
System.out.println("Tokenizing the input file:");
System.out.print(completeStem(tokens1));
}
//method to completely stem the words in an array list
public static ArrayList<String> completeStem(List<String> tokens1){
PorterAlgo pa = new PorterAlgo();
ArrayList<String> arrstr = new ArrayList<String>();
for (String i : tokens1){
String s1 = pa.step1(i);
String s2 = pa.step2(s1);
String s3= pa.step3(s2);
String s4= pa.step4(s3);
String s5= pa.step5(s4);
arrstr.add(s5);
}
return arrstr;
}
//method to tokenize a file
public static ArrayList<String> fileTokenizer(){
StringTokenizer strtoken = new StringTokenizer("this is a book");
ArrayList<String> filetoken = new ArrayList<String>();
while(strtoken.hasMoreElements()){
filetoken.add(strtoken.nextToken());
}
return filetoken;
}
}
Hope this helps you :D