Java Program: Replace Space With "%20" In A String

Here is a java program to replace space with "%20" in a string. For example, the string "We Are Happy" will be changed to "We%20Are%20Happy".
Note that a space is a character while "%20" is a string.

//Replace Space With "%20" In A String
public class Solution {
    public String replaceSpace(StringBuffer str) {
     StringBuffer s = new StringBuffer();
 
  for(int i=0;i<str.length();++i) {
   if (str.charAt(i)==' ') {
    s.append("%20");
   } else {
    s.append(str.charAt(i));
   }
  }
        return s.toString();
    }
}