@@ -0,0 +1,299 @@
+class WithStringBuilder%7B%0A  public static void main(String%5B%5D args)%7B%0A    String%5B%5D fields = %7B%22Hi%22, %22Ha%22, %22Ya%22%7D;%0A    StringBuilder builder = new StringBuilder();%0A    for(String w:fields)%7B%0A      builder.append(w);      %0A    %7D%0A    String result = builder.toString();%0A    System.out.println(result);%0A  %7D%0A%7D%0A

Add class WithStringBuilder.