@@ -0,0 +1,252 @@
+// http://codingbat.com/prob/p165312%0A%0Apublic String doubleChar(String str) %7B%0A    String output = %22%22;%0A    for (int i = 0; i %3C str.length(); ++i) %7B%0A      output += String.valueOf(str.charAt(i)) + String.valueOf(str.charAt(i));%0A    %7D%0A    return output;%0A%7D%0A

Create doubleChar.java