Replacing all matched strings in a file with matcher.replaceall in Java

Question

I am trying to replace only matched strings in a file by using matcher.replaceAll().Like below

public static void main(String[] args) throws IOException, BadLocationException {

      FileInputStream fis = null;
      String output = new Scanner(new File("C:/file.in")).useDelimiter("\\Z").next();//file.in contains HTML text
      String s2 = null;
      StringWriter writer = new StringWriter();
      for (int i=0; i<patternList.size(); i++)//PatternList contains names to be extracted from file
      {
          Matcher matcher = patternList.get(i).matcher(output);
          while (matcher.find()) 
          {
                String matched = matcher.group();//I need to replace only matched strings returned by matcher
                s2=matcher.replaceAll("<span style='background-color:red;'>"+matched+"</span>");
      File file = new File("C:/data/filename.in");
      FileWriter fw = new FileWriter(file.getAbsoluteFile());
        BufferedWriter bw = new BufferedWriter(fw);
        bw.write(s2);
        bw.close();
          }   
      }

The resulting string s2 updated with only last string in PatternList.Each time i am overwriting the string with newly matched string. How can i get the final big string which is updated with all matched strings(names in patternlist).

anubhava · Accepted Answer · 2013-11-21 10:00:16Z

1

I believe you have lot of redundant code. You definitely don't need a list of Pattern objects.

Consider this code:

String output = new Scanner(new File("C:/file.in")).useDelimiter("\\Z").next();
String repl = output.replaceAll("\b(Shannon|Sperling|Kim|Tammy|Nancy|Lana)\b", 
              <span style='background-color:red;'>$1</span>"); 

File file = new File("C:/data/filename.in");
FileWriter fw = new FileWriter(file.getAbsoluteFile());
BufferedWriter bw = new BufferedWriter(fw);
bw.write( repl );
bw.close();

answered Nov 21, 2013 at 10:00

anubhava

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10 Comments

user3004131 Over a year ago

I have just showed 6 strings in the example for simplicity, In reality i have thousands of strings to be updated.That can be achieved only through "matcher". Whenever the match occurs, i need to update it.

anubhava Over a year ago

If you have thousands of keywords even then building a fewer Pattern objects is possible by putting an | between them (as shown above) rather than creating one Pattern/Matcher for each keyword.

user3004131 Over a year ago

Those strings are stored in dictionary, some times they may be multiples of 1000's.I am reading the entry in a dictionary, building a pattern then checking for existance in a file.The way you said does not look like good way.Infact it is not at all possible to get all strings and put it there with "|" as seperator.

anubhava Over a year ago

Every dictionary of words can return your String words so not sure what you're talking about. In your question you have String[] names. Think of reasons why your question is NOT getting any answers.

user3004131 Over a year ago

Your code works fine for replacing strings in a specified file.Because you are replacing all strings in one line and assigning to the result string.But my requirement is different.First i have to get the dictionary entry, build a pattern and use for matcher to get the matched string with START and END index(Which are very important for my project), then just highlight the matched strings in a file.The reason why i should i use Dictionary is they will change constantly.Suppose if i have 3000 names in a dictionary, how it works with your code.

|

user3004131 · Accepted Answer · 2013-11-24 08:47:12Z

I am able to solve the problem after changing s2 to output.Assign the result(matcher.replaceAll) to output instead of s2. Now all the matched strings replaced with color tag.

public static void main(String[] args) throws IOException, BadLocationException {
FileInputStream fis = null;
  String output = new Scanner(new File("C:/file.in")).useDelimiter("\\Z").next();//file.in contains HTML text
  String s2 = null;
  StringWriter writer = new StringWriter();
  for (int i=0; i<patternList.size(); i++)//PatternList contains names to be extracted from file
  {
      Matcher matcher = patternList.get(i).matcher(output);
      while (matcher.find()) 
      {
            String matched = matcher.group();//I need to replace only matched strings returned by matcher
            output=matcher.replaceAll("<span style='background-color:red;'>"+matched+"</span>");
  File file = new File("C:/data/filename.in");
  FileWriter fw = new FileWriter(file.getAbsoluteFile());
    BufferedWriter bw = new BufferedWriter(fw);
    bw.write(output);
    bw.close();
      }   
  }

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