How to retain . dot in java regular expressions

Question

My program is as below,

    /**
     * @param args
     */
    public static void main(String[] args) {
        RegularExpressions r = new RegularExpressions();
        // TODO Auto-generated method stub
        String []input = {" Dear [name],\n",
                "\n",
                "Thanks for buying the [num] [item].\n",
                "We appreciate your patronage\n",
                "\n",
                "Best, [sales_person]\n"};
        HashMap<String, String> dic = new HashMap<String, String>();
        dic.put("name", "Anna Bell Smith");
        dic.put("num", "eight");
        dic.put("item", "Boxes of Soap.");
        dic.put("sales_person", "Karmine Smithe");
        String []afterChange = r.replace(input, dic);
        r.display(afterChange);

    }
    String [] replace(String []strings, Map<String, String> dict){
        String patternStr = ".(";
        for(String key:dict.keySet()){
            patternStr = patternStr + key + "|";
        }
        patternStr = patternStr.substring(0, patternStr.length()-1);
        patternStr = patternStr+").";
        Pattern pattern = Pattern.compile(patternStr);
        for(int i=0;i<strings.length;i++){
            StringBuffer sb = new StringBuffer();
            Matcher matcher = pattern.matcher(strings[i]);
            boolean isMatcherFind = false;
            while(matcher.find()){

            matcher.appendReplacement(sb, dict.get(matcher.group(1)));
                isMatcherFind = true;
            }

            if(isMatcherFind){
                strings[i] = sb.toString();
            }else{
                strings[i] = strings[i];
            }
        }
        return strings; 

    }
    void display(String []str){
        for(String s:str){
            System.out.println(s);
        }
    }
}

The above program is giving an output like

Dear Anna Bell Smith
Thanks for buying the eight Boxes of SoapWe appreciate your patronage
Best, Karmine Smithe

While I am expecting output as

Dear Anna Bell Smith


Thanks for buying the eight Boxes of Soap.
We appreciate your patronage



Best, Karmine Smithe.

Meaning, dot(.) and "\n" should be retained instead it is replacing with empty spaces. I am java 8 version, let me know how can i retain dot(.) and "\n"

Answer 1

You have a loop that repeatedly calls matcher.find() to find the next match in the string; then it calls appendReplacement(). The javadoc for appendReplacement says it does this:

1. It reads characters from the input sequence, starting at the append position, and appends them to the given string buffer. It stops after reading the last character preceding the previous match, that is, the character at index start() - 1.

2. It appends the given replacement string to the string buffer.

3. It sets the append position of this matcher to the index of the last character matched, plus one, that is, to end().

So for each match, it appends the characters up to the match, then it appends the replacement string (instead of the string that got matched). So far, so good.

But what happens when there's no more matches? There are still characters left in the input, to the right of the last match, that didn't get appended to the output.

Fortunately, there's a method that takes care of exactly that for you: appendTail.

Answer 2

You'd have to use appendReplacement and appendTail explicitly. Unfortunately you have to use StringBuffer to do this. Here's a snippet:

    String content="aaaaaaaaaa";
Pattern pattern = Pattern.compile("a");
Matcher m = pattern.matcher(content);

StringBuffer sb = new StringBuffer();
final int N = 3;
for (int i = 0; i < N; i++) {
  if (m.find()) {
     m.appendReplacement(sb, "b");
  } else {
     break;
  }
}
m.appendTail(sb);
System.out.println(sb); // bbbaaaaaaa

according to matcher-replace-method