Jason S Jason S - 1 year ago 89
Java Question

Java: convert List<String> to a String

JavaScript has


js>["Bill","Bob","Steve"].join(" and ")
Bill and Bob and Steve

Does Java have anything like this? I know I can cobble something up myself with StringBuilder:

static public String join(List<String> list, String conjunction)
StringBuilder sb = new StringBuilder();
boolean first = true;
for (String item : list)
if (first)
first = false;
return sb.toString();

...but there's no point in doing this if something like it is already part of the JDK.

Answer Source

All the references to Apache Commons are fine (and that is what most people use) but I think the Guava equivalent, Joiner, has a much nicer API.

You can do the simple join case with

Joiner.on(" and ").join(names)

but also easily deal with nulls:

Joiner.on(" and ").skipNulls().join(names);


Joiner.on(" and ").useForNull("[unknown]").join(names);

and (useful enough as far as I'm concerned to use it in preference to commons-lang), the ability to deal with Maps:

Map<String, Integer> ages = .....;
String foo = Joiner.on(", ").withKeyValueSeparator(" is ").join(ages);
// Outputs:
// Bill is 25, Joe is 30, Betty is 35

which is extremely useful for debugging etc.

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