Java – Porter Stemmer code

javanlpporter-stemmer

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.

Best Solution

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