Question

I am trying to create a map by taking the first character of each word and it’s position in a sentence/paragraph.
I am using regex pattern to achieve this.
Regex is a costly operation.
Are there are any ways to achieve this?

Regex way:

public static void getFirstChar(String paragraph) {
    Pattern pattern = Pattern.compile("(?<=\\b)[a-zA-Z]");
    Map newMap = new HashMap();

    Matcher fit = pattern.matcher(paragraph);
    while (fit.find()) {
        newMap.put((fit.group().toString().charAt(0)), fit.start());
    }
}

Answer 1

You can do your own linear scan if you really need to squeeze every bit of performance:

                 //0123456789012345678901
    String text = "Hello,my name is=Helen";
    Map<Character,Integer> map = new HashMap<Character,Integer>();

    boolean lastIsLetter = false;
    for (int i = 0; i < text.length(); i++) {
        char ch = text.charAt(i);
        boolean currIsLetter = Character.isLetter(ch);
        if (!lastIsLetter && currIsLetter) {
            map.put(ch, i);
        }
        lastIsLetter = currIsLetter;
    }

    System.out.println(map);
    // prints "{n=9, m=6, H=17, i=14}"

API links

• Character.isLetter