在Java 8中使用分隔符连接字符串值并处理空字符串和空字符串? [英] Concatenate string values with delimiter handling null and empty strings in java 8?

问题描述

在Java 8中，我有一些String值，并且我想以逗号分隔的有效值列表结尾.如果字符串为 null或为空，我想忽略它.我知道这似乎很常见，很像

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).

我看过Java 8 StringJoiner，公用StringUtils(联接)和可信赖的番石榴(Joiner)，但似乎都没有一个完整的解决方案.愿景:

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();

将导致niceString ="a，b"

would result in niceString = "a,b"

没有一种好方法(不涉及for循环，将字符串加载到列表中和/或使用regex替换来删除不良条目)吗?

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)?

推荐答案

String joined = 
    Stream.of(val1, val2, val3, val4)
          .filter(s -> s != null && !s.isEmpty())
          .collect(Collectors.joining(","));

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