I heard some are . Well, my journey was a bit different: I moved from Java to Dart. And, part of came with me. moving from JavaScript to Dart adwords.google.com AdWords is and is currently being . But the corner of AdWords I worked on — the part that sells skippable ads on YouTube — has been running Dart since 2014. at the heart of Google’s revenue stream rewritten in Dart The interesting part of the story is that we weren’t told to use Dart, or even asked to use it; we saw what Dart had to offer and decided it was worth a try. Crucially, we didn’t do a big-bang rewrite. We were using , and were able to integrate it with Dart in the browser in order to move to Dart incrementally. As our familiarity with Dart grew, so did our enthusiasm for it; and in the end we rewrote nearly all our browser code from /GWT to Dart. Java/GWT Java Here are the major reasons I found to prefer Dart over Java. 1. The Dart SDK If you’ve written much Java, one of your biggest complaints is probably the SDK libraries. Key decisions were made a long time ago, and can’t be changed. You only have to compare Java’s to Dart’s to see how far things have come. Iterable Iterable So the best way to write Java is to bring in a third party library. At we use , and it’s quite wonderful. For example, it offers . But without being part of the SDK it’s still a second class citizen. Google Guava FluentIterable Dart had the chance to do everything from scratch, and it shows. Here’s an example that you might use FluentIterable for in Java: print([1, 2, 3].where((x) => x.isOdd).map((x) => x + 10));-->(11, 13) try it on dartpad 2. Callbacks, Futures and async/await If you’ve written much Java/GWT, you’ve probably developed an autonomic response to the word “callback”. The merest mention brings you out in a cold sweat. I’ve personally written and maintained terrible, horrible code that threaded callbacks through callbacks through callbacks to deal with different eventualities in chains of RPCs. Here’s a relatively tame example: public void getFoo(AsyncCallback<List<String>> callback) {getThenFilter("foo", callback);} private void getThenFilter(final String parameter,final AsyncCallback<String> callback) {makeRequest(new AsyncCallback<List<String>>() {void handle(List<String> values) {List<String> filtered = new ArrayList<>();for (String value : values) {if (value.startsWith(parameter)) {filtered.add(value);}}callback.handle(filtered);}} And then Dart came along with the class, and an SDK designed around it, and made all that go away. This is when it immediately became clear Dart was talking to . It was providing exactly what I needed to make my day better: Future me, personally Future<List<String>> getFoo() {return _getThenFilter('foo');} Future<List<String>> _getThenFilter(String parameter) {return makeRequest().then((result) =>result.where((string) => string.startsWith(parameter)).toList());} And it didn’t stop there. They talked about adding async/await keywords to Dart as a nicer way to use futures. You could just write “await” and then continue coding the asynchronous code blocked, and everything would be handled for you behind the scenes. as if And then . As a long-time Java developer I had learned to think of discussions about language changes as purely hypothetical, never to impact my work day. I was overjoyed: they actually did it Future<List<String>> getFoo() {return _getThenFilter('foo');} Future<List<String>> _getThenFilter(String parameter) async {var unfiltered = await makeRequest();return unfiltered.where((string) => string.startsWith(parameter)).toList();} try it on dartpad 3. No Nonsense, No Boilerplate Moving from Java to Dart you encounter so many features that just make life easier: Public by default, private by prefixing “_” Collection literals; try them Everything’s an object — no “primitives” Named parameters, optional parameters, defaults; try them Properties — no need to write “get” methods everywhere Cascades — everything’s a builder Type inference with — just write “var” for locals strong mode Named constructors, auto assignment to fields; try them String interpolation, several types of string literal; try them dartfmt — so you don’t have to worries about formatting Gaining just one of these would raise a smile from any Java programmer. The whole lot at once is overwhelming — in a good way. 4. Moving Forward The language improvements didn’t stop with the addition of async/await. We recently got a new . Work is in progress on a non-nullable types experiment. The type system is being revamped with . generic method syntax strong mode Dart is moving forward in a thoroughly pragmatic way: any new feature has to pull its weight in real code. So there will be new stuff — but only good new stuff. 5. Webby Finally, Dart came with UI frameworks that were “webby”. We actually started before AngularDart existed in any form, with . Then we used AngularDart, and now . All of these had something in common: lightweight, HTML-like templates. And it turned out this was a wonderful way to build UI code. Web UI AngularDart 2 The Search for Immutability The only big thing missing from Dart from my point of view was good support for immutable collections and values. So I quickly hacked together something workable for my team to use, in the hope that someone else would write packages I could use. In the end, though, I put in the time to make something worth open sourcing. The and packages were born. built_collection built_value And that’s it. Dart is ready for prime time. You can build huge, mission critical web applications in it, as we did with AdWords for video; or you can take and start building mobile apps for Android and iOS. And as my recent articles have shown, Dart on the server goes with Dart on the client. flutter really well As to my own personal story; shortly after giving a talk at the Dart Developer Summit I joined the Dart team. So in the end I really did “move to Dart”. Update A couple of extra notes following . feedback to this article on Reddit FluentIterable wasn’t a example of needing third party libraries to complement the SDK, as Java 8 adds streams which offer significantly similar functionality. great The next SDK comparison that comes to mind is reading a file. In Dart you can just do “new File(‘foo.txt’).readAsStringSync()”, or “await new File(‘foo.txt’).readAsString()” if you don’t want to block. I always had to look up the current correct way to do this in Java. It’s easy to find more examples, and this shouldn’t come as a surprise: Dart’s SDK was built a long time after Java’s. API design in OO languages has come on long way. I’d like to emphasize that this article is about Dart as compiled to js, for use in the browser. The transition we made was from Java/GWT to Dart. And, finally, I think it’s worth saying that Java is still my favourite of the many languages I’ve worked in. second

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