Dump the fields of a class to a delimited text file so that you can leverage text processing tools like awk, sort, uniq, etc to continue the exploration of your heap dump.
I was exploring a memory leak at work and came across Ryan Cuprak's slides "Exploring Java Heap Dumps" he presented at Oracle Code One 2018. https://www.slideshare.net/rcuprak/exploring-java-heap-dumps-oracle-code-one-2018
Here he goes over how to leverage VisualVM's heap dump analyzer library to extract information. I recommend going over his slides because it provides a good introduction to hprof files and the overall strategy you should apply when trying to extract data from data structures. In the slides, he provides code for extracting Strings, ArrayLists and LinkedLists but you can extend the strategies to apply to HashMaps, TreeMaps, etc.