Sometimes java applications take more than the default allocated amount of memory that is provided to the Java Virtual Machine (JVM).  It's important to note that just because your computer has 2 GB of RAM, java will only ever use what it's told it can.  By default a java process allocates 256MB of RAM, often times this is not enough and must be increased.  Otherwise you will likely see an error message/exception that looks similar to this:

"java.lang.OutOfMemoryError: Java heap space"

The JVM has many "pools" of memory.  The "heap" is one of those pools of memory.  In a way these different pools of memory are modeled similar to short and long term memory in people.  In that data in the "short term memory" often contains garbage that you don't need to remember.  Things that are useful to remember are moved from the short term memory to the long term memeory.

When you start up java,  it allocates memory to the JVM by the "heap size" setting.  You can change these settings when you start java by passing additional command line arguments to the java process when it start.

For example by default you would start MyRobotLab like this

java -jar myrobotlab.jar

However, lets say you want to give MyRobotLab 2 GB of ram when you start it up so you avoid the "OutOfMemoryError", you can do this by specifying the java parameter  "-Xmx" and passing it the desired memory allocation in a format like  256m  (for 256 megabytes of ram) or 2g  (for 2 gigabytes of ram) 

the full command would then look like this:

java -Xmx2g -jar myrobotlab.jar

When the JVM starts up, it will allocated up to 2gb of ram to the java application before throwing the dreaded OutOfMemoryError.

Now, there is another type of memory pool called the "permenent generation" memory, or more commonly known as PermGen.  If you see an error message like this, it means that you're out of a different "pool" of memory 

java.lang.OutOfMemoryError: PermGen space

The "PermGen" memory is where Java loads all of the Jar files.  When a java process starts up, all of the Jar files in the class path are loaded into the PermGen memory space (I believe this is a lazy load, someone with more knowledge of the JVM internals can correct me on this.)  If there are a lot of JAR files to load, it's possible that you could run out of PermGen memory, and this means you need to increase the PermGen memory size.  That can be done with the "-XX:MaxPermSize="

By default,  I think 128MB of ram is allocated to the PermGen memory space.  To increase this you can add the commnad line argument to java to increase it as folows:

java -XX:MaxPermSize=512m -jar myrobotlab.jar

This would allocate additional memory for loading additional jar files and libraries into MRL.

The topic of JVM memory settings and Garbage Collection Tuning are quite expansive, for brevity,  I have included the key commands to increase the settings.  There are tuning parameters for how large the pools are and how objects get moved from the "short term" or "early generation" pools into the "long term" or "older generation" memory pools.

Hope this info was useful, happy roboting!