Exception in thread “main” java.lang.OutOfMemoryError: Java heap space

When this exception occurs, it means java runs out of memory.

You can increase memory(heap size) by run java including these parameters:

-Xms[initial heap size] -Xmx[maximum heap size]

For example, set initial heap size to 128m and maximum to 256m.

java -Xms128m -Xmx256m

In NetBeans, simply goes to Project Properties –> Run.
Then you can add these parameters in VM Options.