private Integer maybeIndex(String name, Tuple tuple) {
		Integer index = null;
		try {
			int i = Integer.parseInt(name);
			if (i > -1 && tuple.size() > i) {
				index = i;
			}
		}
		catch (NumberFormatException e) {
			// not an integer
		}
		return index;
	}
Return an integer if the String property name can be parsed as an int, or null otherwise.
spring-xd-tuple/src/main/java/org/springframework/xd/tuple/spel/TuplePropertyAccessor.java