在java 8中使用分隔符处理空字符串和空字符串连接字符串值？
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Concatenate string values with delimiter handling null and empty strings in java 8?
提问by eze
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 emptyI 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).
在 Java 8 中，我有一些字符串值，我想以逗号分隔的有效值列表结束。如果 String 为null 或空，我想忽略它。我知道这似乎很常见，而且很像这个老问题；但是，该讨论并未解决空值和空格（我也不喜欢接受的答案）。
I've looked at Java 8 StringJoiner, commons StringUtils (join) and trusty guava (Joiner) but none seems like a full solution. The vision:
我看过 Java 8 StringJoiner、commons StringUtils (join) 和 trusty guava (Joiner) 但似乎没有一个是完整的解决方案。愿景：
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"
会导致 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)?
难道没有一个很好的方法来做到这一点（不涉及 for 循环、将字符串加载到列表中和/或正则表达式替换以删除错误条目）？
采纳答案by Brian Goetz
String joined =
Stream.of(val1, val2, val3, val4)
.filter(s -> s != null && !s.isEmpty())
.collect(Collectors.joining(","));
