Remove space character

Question

I have a string. I want to replace the first occured space character after a valid character in comma character and the following space character I want to remove them.
ex: "a b c d e" => "a,b,c,d,e"
the string method replace(char, char) cannot do replace(' ', '')
can somebody help me?
thank you.

Answer 1

import java.util.regex.*;
class B  {
   public static void main(String[] args) {
     String INPUT = "a b c         d   e";
     String REGEX = "\\b\\s+\\b";
    Pattern p = Pattern.compile(REGEX);
    Matcher m = p.matcher(INPUT);
    StringBuffer sb = new StringBuffer();
    while(m.find()){
             String REPLACE = ",";
             m.appendReplacement(sb,REPLACE);
        m.appendTail(sb);
        System.out.println(sb.toString());
}