Scala REPL: java.lang.OutOfMemoryError: Java heap space error

I just got a “java.lang.OutOfMemoryError: Java heap space error” when trying to use the Scala REPL to analyze a large XML dataset, as shown here:

$ scala
Welcome to Scala version 2.10.0 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_37).
Type in expressions to have them evaluated.
Type :help for more information.

scala> import scala.xml._
import scala.xml._

scala> val xml = XML.loadFile("nasa.xml")
java.lang.OutOfMemoryError: Java heap space

Solution: Control the REPL memory use

In short, I solved this problem by starting the Scala REPL with this command to control the RAM usage:

$ scala -J-Xms256m -J-Xmx512m

An alternative way to start the REPL is this:

$ env JAVA_OPTS="-Xms256m -Xmx512m" scala

The scala man page has a little more information on this memory-related commands:

With Java 1.5 (or newer) one may for example configure the memory usage  
of the JVM as follows:

    JAVA_OPTS="-Xmx512M -Xms16M -Xss16M"

With GNU Java one may configure the memory usage of the GIJ as follows: 

    JAVA_OPTS="--mx512m --ms16m"

In summary, if you are getting a “java.lang.OutOfMemoryError: Java heap space error” when trying to use the Scala REPL, I hope this has been helpful.

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