# Ruby/Java strings solved the Ruby way **URL:** \ **Category:** Ruby\ **Created:** [July 20, 2008, 8:08pm UTC](https://www.ruby-forum.com/t/ruby-java-strings-solved-the-ruby-way/143578 "2008-07-20T20:08:42Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![headius](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/7c8e57/32.png) [@headius](https://www.ruby-forum.com/u/headius)\ **Post date:** [July 20, 2008, 8:08pm UTC](https://www.ruby-forum.com/t/ruby-java-strings-solved-the-ruby-way/143578/1 "2008-07-20T20:08:42Z")
Hello all! I’m posting this here because it seem like a topic better discussed in the general Ruby community. JRuby allows you pretty seamless access to Java libraries through its Java integration layer. You can pull in just about any class, instantiate objects, call methods, and so on. In order to make this a bit easier, in many cases we automatically coerce particular Ruby types to their equivalent Java types. For example, Fixnum becomes either boxed integral or primitive integral values, Floats become boxed floating-point or primitive floating point values, and Strings are decoded from byte[] into Java String as UTF-8. But there’s a problem with this…it adds a bit of overhead in the numeric cases, and a _lot_ of overhead in the String case. Here’s a comparison between calling a method that takes an int and a method that takes a String (best times out of five): with string ‘hello’: 1.068688 with fixnum 1: 0.563014 And this is a short string. The coercion cost for strings is at least O(n). It’s about String coercion I’m writing. We’ll never be able to eliminate the coercion cost entirely. Ruby Strings are byte[] and it has been a great move for us implementing our own String and related classes to use byte[] always. So there’s never going to be a straight-through path from a Ruby String to a Java String. But I think we can reduce the impact for JRuby users by doing things the Ruby way. Ruby already has a protocol for coercion, via methods like to\_str, to\_ary and so on. This allows you to pass e.g. non-Strings to methods that act on Strings, and frequently (usually) they’ll coerce and work fine. Often, if you want to avoid a coercion hit, you’ll create the String ahead of time. And that’s where we can learn from Ruby for Java String handling. So I propose that instead of always decoding incoming Ruby String into a Java String when calling a Java method, we introduce a new type–call it JString for now–that represents a Java string. When you require in the Java integration support, it would add to Ruby String a method to\_jstring (or to\_String or hey, toString?). So for calls from Ruby to Java, we’d follow Ruby coercion protocols and only accept either JString or objects that coerce to JString. Likewise, coming from Java to Ruby, we wouldn’t automatically coerce; we’d return a JString object that implements to\_str. You can then usually pass that to String APIs, or just coerce it immediately and go on with your business. Since this latter change would break some apps that expect Java strings to always be coerced, it would be saved for the next major release of JRuby and thoroughly discussed. I think this model provides the best possible experience when calling Java from Ruby but also allow JRuby users to take control of the coercion process, either be defining their own to\_jstring methods on other types, or by pre-coercing strings they intend to use a lot. Thoughts? - Charlie ---
**Author:** ![headius](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/7c8e57/32.png) [@headius](https://www.ruby-forum.com/u/headius)\ **Post date:** [July 21, 2008, 9:28pm UTC](https://www.ruby-forum.com/t/ruby-java-strings-solved-the-ruby-way/143578/2 "2008-07-21T21:28:21Z")
On Sun, Jul 20, 2008 at 1:36 PM, Charles Oliver N. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: [snip] > that to String APIs, or just coerce it immediately and go on with your > business. Since this latter change would break some apps that expect Java > strings to always be coerced, it would be saved for the next major release > of JRuby and thoroughly discussed. This sounds like an excellent compromise. I vote for to\_jstring because it looks most Ruby-esque. Jim ---
**Author:** ![headius](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/7c8e57/32.png) [@headius](https://www.ruby-forum.com/u/headius)\ **Post date:** [July 21, 2008, 11:13pm UTC](https://www.ruby-forum.com/t/ruby-java-strings-solved-the-ruby-way/143578/3 "2008-07-21T23:13:59Z")
Jim M. wrote: > > Likewise, coming from Java to Ruby, we wouldn’t automatically coerce; we’d > > return a JString object that implements to\_str. You can then usually pass > > that to String APIs, or just coerce it immediately and go on with your > > business. Since this latter change would break some apps that expect Java > > strings to always be coerced, it would be saved for the next major release > > of JRuby and thoroughly discussed. > > This sounds like an excellent compromise. I vote for to\_jstring > because it looks most Ruby-esque. Also up for debate is whether boxed primitives from Java should behave the same way, with a JInteger, JFloat, and so on that can coerce to Fixnum or Float. But boxed primitives are considerably cheaper to coerce than Strings, so it may not be worth it. - Charlie