This is how my map looks like.

```
Map<String, String> maps = List.stream().collect(Collectors.toMap(Cat::getName, Cat::getNumber, (c1,c2) -> c1));

```

If I already have "Lucy, 101" in maps then I am unable to add another value corresponding to the name Lucy i.e "Lucy, 102". Is there any way to change the merge function [ (c1,c2) -> c1 ] so that I can have two values corresponding to a single key (Lucy) in my maps?