mystery5 method
public static String replace(String str, String find, String replacement)
{
if(str.length() < find.length())
return str;
if(str.substring(0, find.length()).equals(find))
return replacement + replace(str.substring(find.length()), find, replacement);
else
return str.substring(0, 1) + replace(str.substring(1), find, replacement);
}
The method replaces all occurrences of find with replacement.
The base case and the conditional statement are the same as mystery4/countMatches. If str starts with find, the method is called again with find removed from the beginning of str. replacement is appended to the beginning of result of the call. If str does not start with find, a single character is removed from str (and replaced after the call).