Double brace initialisation (anonymous inner class) with diamond operator

Question

I am wondering why the second map declaration (using the diamond operator) does not compile when the first one does. Compilation error:

error: cannot

Answer 1

Diamond inference doesn't work for instantiating anonymous classes, which is what you're doing here.

Try this:

Map map1 = new HashMap<>();

{
    map1.put("abc", "abc");
}