Sunday, March 20, 2016

Java 8: Joining a Stream

In a previous post, I wrote about how you can use Guava's Joiner to easily convert an Iterable into a String, so you no longer have to iterate over it and build the String manually.

Java 8 introduces the StringJoiner, which can be used to join a Stream using Collectors.joining. For example:

Arrays.asList("apple", "banana", "cherry")
      .stream()
      .collect(Collectors.joining(", ");

To skip nulls and empty strings, you can filter the stream first:

Arrays.asList("apple", "banana", null, "", "cherry")
      .stream()
      .filter(s -> s != null && !s.isEmpty())
      .collect(Collectors.joining(", ");

I'd still use Guava's Joiner for lists though.

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