Agile Fusion

Mobile phone is a resource constrained device, that imposes some challenges for application developers.

Quite often it is very convenient to use multidimensional arrays, though when doing so, we have to keep in mind that there is an overhead price to pay, that is, for every array object created, overhead == 16 bytes.
int array of size:0 uses 16 bytes of heap
int array of size:1 uses 20 bytes of heap
int array of size:2 uses 24 bytes of heap

For large data structures built with multidimensional arrays, you can oftentimes reduce the extra dimension overhead by an easy indexing change: convert every int[dim1][dim2] instance to an int[dim1*dim2] instance and change all expressions like a[i][j] to a[i*dim2 + j]. Of course, you pay a price from the lack of index-range checking on dim1 dimension (which also boosts performance).

For more tips on memory optimization, see javaworld’s java tip 130.