Join strings with different separators in Java

Question

I have a list of strings, e.g. days of the week. And I'd like to join them on comma, with "and" before the last element. E.g: "I'm available on Tue, Wed, Thu and Fri".

Something elegant like

Joiner.on(", ").join(days)

Does not work. Is there an elegant way to do it with Guava or similar library?

Thanks

Answer 1

There is no straightforward solution, but you may consider mine:

final String COMMA = ", ", AND = " and ";
List<String> list = Arrays.asList("Tue", "Wed", "Thu", "Fri");
int last = list.size() - 1;

Joiner.on(AND).join(
    list.stream().limit(last).collect(joining(COMMA)),
    list.get(last)); // Tue, Wed, Thu and Fri

The another shorter way is:

list.stream().limit(last).collect(joining(COMMA, "", AND))
    .concat(list.get(last));

These methods perfectly work for 2+ days.

Edge cases (list == null || list.isEmpty() and list.size() < 2) may be handled by the if statements.

Answer 2

Considering you're "not Java 8 friendly at this moment" (you probably mean lambdas and streams), how about using StringJoiner:

public static String join(List<String> parts, String delimiter, String lastDelimiter) {
    StringJoiner joiner = new StringJoiner(delimiter, "", lastDelimiter);

    for (int i = 0; i < parts.size() - 1; i++) {
        joiner.add(parts.get(i));
    }

    return joiner.toString() + parts.get(parts.size() - 1);
}

However, doing the same with streams:

public static String join(List<String> parts, String delimiter, String lastDelimiter) {
    return parts.stream()
            .limit(parts.size() - 1)
            .collect(Collectors.joining(delimiter, "", lastDelimiter))
            .concat(parts.get(parts.size() - 1));
}

EDIT: Just found String#join(CharSequence, Iterable<? extends CharSequence>):

public static String join(List<String> parts, String delimiter, String lastDelimiter) {
    return String.join(delimiter, parts.subList(0, parts.size() - 1)) 
            + lastDelimiter + parts.get(parts.size() - 1);
}

In order to handle corner cases I'd go for Xaerxess switch solution.