问题
In Java 8 I have some number of String values and I want to end up with a comma delimited list of valid values. If a String is null or empty I want to ignore it. I know this seems common and is a lot like this old question; however, that discussion does not address nulls AND spaces (I also don't like the accepted answer).
I've looked at Java 8 StringJoiner, commons StringUtils (join) and trusty guava (Joiner) but none seems like a full solution. The vision:
where: val1="a", val2=null, val3="", val4="b"
String niceString = StringJoiner.use(",").ignoreBlanks().ignoreNulls()
.add(val1).add(val2).add(val3).add(val4).toString();
would result in niceString = "a,b"
Isn't there a nice way to do this (that doesn't involve for loops, loading strings into a list, and/or regex replaces to remove bad entries)?
回答1:
String joined =
Stream.of(val1, val2, val3, val4)
.filter(s -> s != null && !s.isEmpty())
.collect(Collectors.joining(","));
来源：https://stackoverflow.com/questions/36705880/concatenate-string-values-with-delimiter-handling-null-and-empty-strings-in-java