code: public static void callStringBuilderLength(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, "length", TypeDesc.INT, null);
      }
docs: Calls length on a StringBuilder on the stack, leaving an int on the stack.