program to put HTML links around URLs strings | java

import java.util.*;
import java.io.*;

public class URLify {
  public static char[] URLify(char[] chars, int len) {
    int spaces = countSpaces(chars, len);
    int end = len - 1 + spaces * 2;
    for (int i = len - 1; i >= 0; i--) {
      if (chars[i] == ' ') {
        chars[end - 2] = '%';
        chars[end - 1] = '2';
        chars[end]     = '0';
        end -= 3;
      } else {
        chars[end] = chars[i];
        end--;
      }
    }
    return chars;
  }

  static int countSpaces(char[] chars, int len) {
    int count = 0;
    for (int i = 0; i < len; i++)
      if (chars[i] == ' ')
        count++;
    return count;
  }

  public static void main(String[] args) throws IOException {
    char[] chars = "Mr John Smith    ".toCharArray();
    System.out.println(URLify(chars, 13));
  }
}