Java > Recursion-1 > pairStar (CodingBat Solution)

Problem:

Given a string, compute recursively a new string where identical chars that are adjacent in the original string are separated from each other by a "*".

pairStar("hello") → "hel*lo"
pairStar("xxyy") → "x*xy*y"
pairStar("aaaa") → "a*a*a*a"

Solution:

public String pairStar(String str) {
  if (str.equals("") || str.length() == 1) return str;
  if (str.charAt(0) == str.charAt(1)) 
    return str.charAt(0) + "*" + pairStar(str.substring(1));
  else
    return str.charAt(0) + pairStar(str.substring(1));
}