In Java 8 you can use Stream:
List<String> list = Arrays.asList("I", " ", "love", null, "you");
String message = list.stream().filter(StringUtils::isNotBlank)
.collect(Collectors.joining(", "));
System.out.println("message = " + message);
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…