How to remove elements of one map from another map?

Question

HashMap<String, String> foo = new HashMap<String, String>();
HashMap<String, String> baar = new HashMap<String, String>();

How to remove items found in baar from foo?

Answer 1

You can try:

foo.keySet().removeAll(baar.keySet())

Changes to a Map's keySet() are reflected in the map itself.

If you want to remove exact mappings (not just based on keys), you can use the same approach with the entrySet() instead:

foo.entrySet().removeAll(baar.entrySet());