2.2 Running the example 3
> scalac HelloWorld.scala
This will generate a few class files in the current directory. One of them will be called
HelloWorld.class, and contains a class which can be directly executed using the
scala command, as the following section shows.
2.2 Running the example
Once compiled, a Scala program can be run using the scala command. Its usage is
very similar to the java command used to run Java programs, and accepts the same
options. The above example can be executed using the following command, which
produces the expected output:
> scala -classpath . HelloWorld
Hello, world!
3 Interaction with Java
One of Scala’s strengths is that it makes it very easy to interact with Java code. All
classes from the java.lang package are imported by default, while others need to
be imported explicitly.
Let’s look at an example that demonstrates this. We want to obtain and format the
current date according to the conventions used in a specific country, say France
1
.
Java’s class libraries define powerful utility classes, such as Date and DateFormat.
Since Scala interoperates seemlessly with Java, there is no need to implement equiv-
alent classes in the Scala class library–we can simply import the classes of the cor-
responding Java packages:
import java.util.{Date, Locale}
import java.text.DateFormat
import java.text.DateFormat._
object FrenchDate {
def main(args: Array[String]) {
val now = new Date
val df = getDateInstance(LONG, Locale.FRANCE)
println(df format now)
}
}
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Other regions such as the french speaking part of Switzerland use the same conventions.