JVM will throw OutOfMemoryError when:
-A new object is to be created
-JVM heap memory(defined by -Xmx) is full
-A full garbage collection isn't able to free enough space to be allocated to the new object.
The concurrent collector will throw an OutOfMemoryError if too much time is being spent in garbage collection: if more than 98% of the total time is spent in garbage collection and less than 2% of the heap is recovered, an OutOfMemoryError will be thrown. This feature is designed to prevent applications from running for an extended period of time while making little or no progress because the heap is too small. If necessary, this feature can be disabled by adding the option -XX:-UseGCOverheadLimit to the command line.