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comparing keys of two hashmaps

Mohit Sinha
Ranch Hand

Joined: Nov 29, 2004
Posts: 125
Hi All,

I want to identify the identical keys amongst two haspmaps (H1 and H2).
Also I need to identify elements of H1 not available in H2 and vice versa.

Currently I am using the HashMap interface containsKey method but have to do something like this

- loop throught all keys of H1 and H2.containsKey(h1_key)
- loop throught all keys of H2 and H1.containsKey(h2_key)

Ist there a better view to implement the same.


Pat Farrell

Joined: Aug 11, 2007
Posts: 4659

If you use the Google Collections package, it has functions to do the usual intersection, union, and difference functions for sets.
Vivek K Singh
Ranch Hand

Joined: Dec 22, 2009
Posts: 85

You do not need to loop thru both the maps, you can do something like:

This will get all keys from the hashmap1 and compare to the hashmap2 and print duplicates...

Rob Spoor

Joined: Oct 27, 2005
Posts: 19908

Or use keySet() in combination with the bulk operators:

How To Ask Questions How To Answer Questions
I agree. Here's the link:
subject: comparing keys of two hashmaps