How to remove elements of one map from another map?

Question

``` HashMap foo = new HashMap(); HashMap baar = new HashMap(); ``` How to remove items found in `baar` from `foo`?

Accepted Answer

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());
```

Solution