Calling Java APIs

Calling Java APIs from Scala is completely seamless. I will demonstrate this functionality by copying data from a URL to a file and then making a copy of that file.

Important Note: Scala 2.8 is getting a redesigned API for accessing files and streams based on JSR-203 New NIO. It is quite nice to use. For example File("/tmp") / "dir" / "dir2" will create a file to /\
tmp/dir/dir2. That is just the most basic of what you can expect. I will do a couple topics on that when it gets closer to being finalized.

1. scala> import java.net._
2. import java.net._
4. scala> import scala.io._
5. import scala.io._
7. scala> import java.io.{File, FileWriter}
8. import java.io.{File, FileWriter}
10. scala> val in = Source.fromURL("http://www.google.com")
11. in: scala.io.Source = non-empty iterator
13. scala> // Until scala 2.8 we have to use the standard java streams and idioms
15. scala> val out = new FileWriter("/tmp/daily-scala")
16. out: java.io.FileWriter = java.io.FileWriter@71d0e17a
18. scala> try {
19.     | out.write( in.getLines.mkString("\n") )
20.     | }finally{
21.     | out.close
22.     | }
24. scala> // now lets copy the file
26. scala> val copy = new FileWriter("/tmp/copy")
27. copy: java.io.FileWriter = java.io.FileWriter@7bfd25ce
29. scala> try {
30.     | copy.write( Source.fromFile("/tmp/daily-scala").getLines.mkString("\n") )
31.     | } finally {copy.close}
33. scala> val copy2 = new FileWriter("/tmp/copy2")
34. copy2: java.io.FileWriter = java.io.FileWriter@7bfd25ce
36. // You can reuse a source if you reset it
37. scala> try {
38.     | copy2.write( in.reset.getLines.mkString("\n") )
39.     | } finally {copy2.close}
41. // Change all 'e' to upper case.  We could write this to a file if we desired
42. scala> in.reset.getLines.mkString("\n").map( c => if (c == 'e') c.toUpperCase else c).mkString("")
43. res9: String = This is thE dEmo filE