code: public static void callStringBuilderAppendChar(CodeBuilder b) {
          // Because of JDK1.5 bug which exposes AbstractStringBuilder class,
          // cannot use reflection to get method signature.
          TypeDesc stringBuilder = TypeDesc.forClass(StringBuilder.class);
          b.invokeVirtual(stringBuilder, "append", stringBuilder, new TypeDesc[] {TypeDesc.CHAR});
      }
docs: Appends a char to a StringBuilder. A StringBuilder and char must be on
  the stack, and a StringBuilder is left on the stack after the call.