Eclipse Memory Analyser

That is probably by far the best heapdump analyser tool I've ever used. It provides immediate suggestions to problem but as well allows to drill into details of heap and navigate object tree. Understand how much memory data structure utilise.

There are number of good articles on the subject. One of the good intro articles here.

I've found that I had to run tool with increased memory on Mac in order to open large heaps. To run it on Mac with extended memory (below is 6Gb) execute following command:

open -a mat --args -vmargs -Xmx6G

Hope it helped someone...