Fix for 5015163, and my first webrev (original) (raw)

Rémi Forax forax at univ-mlv.fr
Sat Feb 7 01:01:39 UTC 2009

Kevin Bourrillion a écrit :

Hello,

A few thoughts. First, this functionality is badly needed. Absolutely everyone rewrites this, in hundreds of different ways. At Google we're no exception, we have our own hand-rolled Join.java class full of static methods, and it has thousands of callers in our private codebase. Your selection of overloads (Iterable, Object[], and (Object,Object...)) is exactly correct. Kudos. We'd added Iterator versions as well, but almost no one uses them, so forget that. My main concerns with your current API are: * I don't think that ",".join(collection) is a good idea. It clashes too strongly with the StringBuilder etc. versions. It also plain "looks weird". A static String.join(",", collection) is preferable. I don't think anyone would be surprised by this. Use the receiver or not: Pro:

Cons:

I'm convinced, I will modify the patch.

* It should be considered separately whether to support other Appendables via static methods (somewhere) like:

static A join(A appendable, String delimiter, Iterable<?> tokens) throws IOException This provides a superset of what your StringBuilder etc. methods can do, but your methods are still good because of their convenience especially in chains of method calls, and because they don't need to throw any exception. Or perhaps, in JDK8 (when closure will be integrated) the compiler will be able to infer that because join is used with String, it can't throw an IOE That's not what BGGA propose but I will love to see that :) But that's another story. * The biggest problem we've had with our Join class is that it turns out that everyone has a different idea of how they'd like nulls handled. - output as "null" (your, and our, current behavior) - skip? - skip only if trailing? - throw NPE? (often the best thing)

In my opinion (i am perhaps wong) join will be mostly used just before print the String. That's why I have chosen the the print(ln) behavior.

We now support everyone by having the concept of an instantiable Joiner (I've seen this in other languages). Example:

private static final Joiner JOINER = Joiner.with(", ").skipNulls(); . . . return JOINER.join("Harry", "Ron", "Hermione"); Just to give everyone food for thought, our Joiner's API currently looks like this: static Joiner with(String separator) Joiner skipNulls() Joiner useForNull(String nullText) A appendTo(A appendable, Iterable<?> parts) throws IOException A appendTo(A appendable, Object[] parts) throws IOException A appendTo(A appendable, Object first, Object... rest) throws IOException StringBuilder appendTo(StringBuilder builder, Iterable<?> parts) StringBuilder appendTo(StringBuilder builder, Object[] parts) StringBuilder appendTo(StringBuilder builder, Object first, Object... rest) String join(Iterable<?> parts) String join(Object[] parts) String join(Object first, Object... rest) MapJoiner withKeyValueSeparator(String keyValueSeparator) class MapJoiner { A appendTo(A appendable, Map map) throws IOException StringBuilder appendTo(StringBuilder builder, Map map) String join(Map map) MapJoiner useForNull(String nullText) } End of random thoughts.

Cool, i don't think this should be integrated in the JDK, After all, If i want a full featured joiner, I can download the google collection jar :)

-- Kevin Bourrillion @ Google internal: http://go/javalibraries google-collections.googlecode.com google-guice.googlecode.com Rémi

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