Breaking a string into substrings

Question

I wrote some code which divides a line through the words of the text so that each substring is no longer than MaxWidth. It works well, but it's very slow.

Pattern pattern = Pattern.compile("(.{1," + symbols + "}(\\b|\\s))"); // symbols - MaxWidth
Pattern pattern2 = Pattern.compile("\\s.*");
while ((line = in.readLine()) != null) { // reading file by lines 
 String dopLine = "";
 if (pattern2.matcher(line).matches()) {
 // If a line begins with a space, it is the beginning of a paragraph and need to add \ n
 if(!tempDopLine.equals("")) { // tempDopLine - Some part of the previous line, which is not full screen
 tempStringBuffer.append(tempDopLine);
 tempStringBuffer.append("\n");
 lineCounter++;
 if (lineCounter == lines) {
 addPage(tempStringBuffer); // create page
 tempStringBuffer = new StringBuilder("");
 lineCounter = 0;
 numberOfPages++;
 }
 }
 tempDopLine = "";
 dopLine = line;
 } else { 
 dopLine = tempDopLine + " " + line; // if this line
 }
 Matcher matcher = pattern.matcher(dopLine); // divide a string into a substrings
 HashMap<Integer, String> temp = new HashMap<Integer, String>();
 int i = 0;
 while (matcher.find()) {
 temp.put(i, matcher.group());
 i++;
 }
 for(i = 0; i < temp.size(); i++) {
 if (i<(temp.size()-1)) {
 String tempL = temp.get(i);
 tempStringBuffer.append(tempL);
 tempStringBuffer.append("\n");
 lineCounter++;
 if (lineCounter == lines) {
 addPage(tempStringBuffer);
 tempStringBuffer = new StringBuilder("");
 lineCounter = 0;
 numberOfPages++;
 }
 } else {
 tempDopLine = temp.get(i); // The last part of the string remember to display it along with the next line
 }
 } 
}

Answer 1

Few thought,

You do a while loop ( while( matcher.find() ) to find all matchs, then you do a for loop to deal with it. I think that can be done in only one loop.

in you last for loop, you could remove the first if :

 for(i = 0; i < (temp.size() -1); i++) {
 String tempL = temp.get(i);
 tempStringBuffer.append(tempL);
 tempStringBuffer.append("\n");
 lineCounter++;
 if (lineCounter == lines) {
 addPage(tempStringBuffer);
 tempStringBuffer = new StringBuilder("");
 lineCounter = 0;
 numberOfPages++;
 }
 } // End for loop
 tempDopLine = temp.get(temp.size()-1); 
} 

Other suggestion the HashMap temp got be only a array, because right now your code do a lot of autoboxing ( from int to Integer) add and to retrieve information from your HashMap.

Edit: Here a quick example to merge your two loops:

String tempL = matcher.group();
while (matcher.find()) {
 tempStringBuffer.append(tempL);
 tempStringBuffer.append("\n");
 lineCounter++;
 if (lineCounter == lines) {
 addPage(tempStringBuffer);
 tempStringBuffer = new StringBuilder("");
 lineCounter = 0;
 numberOfPages++;
 }
 tempL = matcher.group();
} 
tempDopLine = tempL; 

• Anton: To combine the two loop I need to get the number of elements found in the Matcher. How to do it? In my code - last match must writing to tempDopLine
• Anton: Thank you very mych. I using this, but it did not give a large increase in performance. It seems to me that such a low rate because of the regular expressions. They can be something like speed?