Removing consecutive duplicates words out of text using Regex and displaying the new text

Question

Hy,

I have the following code:

import java.io.*;
import java.util.ArrayList;
import java.util.Scanner;
import java.util.regex.*;

/
public  class RegexSimple4
{

     public static void main(String[] args) {   

          try {
              Scanner myfis = new Scanner(new File("D:\\myfis32.txt"));
              ArrayList <String> foundaz = new ArrayList<String>();
              ArrayList <String> noduplicates = new ArrayList<String>();

              while(myfis.hasNext()) {
                  String line = myfis.nextLine();
                  String delim = " ";
                  String [] words = line.split(delim);

                  for (String s : words) {                    
                      if (!s.isEmpty() && s != null) {
                          Pattern pi = Pattern.compile("[aA-zZ]*");
                          Matcher ma = pi.matcher(s);

                          if (ma.find()) {
                              foundaz.add(s);
                          }
                      }
                  }
              }

              if(foundaz.isEmpty()) {
                  System.out.println("No words have been found");
              }

              if(!foundaz.isEmpty()) {
                  int n = foundaz.size();
                  String plus = foundaz.get(0);
                  noduplicates.add(plus);
                  for(int i=1; i<n; i++) {   
                      if ( !noduplicates.get(i-1) .equalsIgnoreCase(foundaz.get(i))) {
                          noduplicates.add(foundaz.get(i));
                      }
                  }

                  //System.out.print("Cuvantul/cuvintele \n"+i);

              }
              if(!foundaz.isEmpty()) { 
                  System.out.print("Original text \n");
                  for(String s: foundaz) {
                      System.out.println(s);
                  }
              }
              if(!noduplicates.isEmpty()) {
                  System.out.print("Remove duplicates\n");
                  for(String s: noduplicates) {
                      System.out.println(s);
                  }
              }

          } catch(Exception ex) {
              System.out.println(ex); 
          }
      }
  }

With the purpose of removing consecutive duplicates from phrases. The code works only for a column of strings not for full length phrases.

For example my input should be:

Blah blah dog cat mice. Cat mice dog dog.

And the output

Blah dog cat mice. Cat mice dog.

Sincerly,

Answer 1

First of all, the regex [aA-zZ]* doesn't do what you think it does. It means "Match zero or more as or characters in the range between ASCII A and ASCII z (which also includes [, ], \ and others), or Zs". It therefore also matches the empty string.

Assuming that you are only looking for duplicate words that consists solely of ASCII letters, case-insensitively, keeping the first word (which means that you wouldn't want to match "it's it's" or "olé olé!"), then you can do that in a single regex operation:

String result = subject.replaceAll("(?i)\\b([a-z]+)\\b(?:\\s+\\1\\b)+", "$1");

which will change

Hello hello Hello there there past pastures 

into

Hello there past pastures 

Explanation:

(?i)     # Mode: case-insensitive
\b       # Match the start of a word
([a-z]+) # Match one ASCII "word", capture it in group 1
\b       # Match the end of a word
(?:      # Start of non-capturing group:
 \s+     # Match at least one whitespace character
 \1      # Match the same word as captured before (case-insensitively)
 \b      # and make sure it ends there.
)+       # Repeat that as often as possible

See it live on regex101.com.

Answer 2

Bellow code work fine

import java.util.Scanner;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

public class DuplicateRemoveEx {

public static void main(String[] args){

    String regex="(?i)\\b(\\w+)(\\b\\W+\\1\\b)+";
    Pattern p = Pattern.compile(regex,Pattern.CASE_INSENSITIVE);

    Scanner in = new Scanner(System.in);
    int numSentences = Integer.parseInt(in.nextLine());
    while(numSentences-- >0){
        String input = in.nextLine();
        Matcher m = p.matcher(input);
        while(m.find()){
            input=input.replaceAll(regex, "$1");
        }
        System.out.println(input);
    }
    in.close();
}

}