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Asked: 2026-05-19T04:05:31+00:00

Let’s say I have 2 Map’s in Java. I want to compare map1’s keys

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Let’s say I have 2 Map’s in Java. I want to compare map1’s keys to map2’s keys to see if there are any similar keys in the 2 maps.

How can i do that?

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1 Answer

  1. Editorial Team

    If you don’t want to modify the maps:

    boolean thereAreCommonKeys = !Collections.disjoint(one.keySet(), two.keySet());

    Finding the common keys:

    Set<K> commonKeys = new HashSet<K>(one.keySet());
commonKeys.retainAll(two.keySet());

    If your keys are dates, they should probably be something Comparable, in which case you might want a TreeSet instead of a HashSet, because it will keep them in order.

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