Type mismatch error in initialization of HashMap>

Question

Since using generics is a good practice in initialing HashMap and the following initialization works fine:

Map<String,String> x = new HashMap<String,String>();

Why do I have a type mismatch error in initialing the nested HashMaps:

Map<String,Map<String,String>> y = new HashMap<String,HashMap<String,String>>();

I use this data structure for generalization of my SQL queries. — Noviff, Jan 21 '17 at 14:32

Maheshwar Ligade · Accepted Answer · 2017-01-21T07:03:43.280

There is an issue with declaration please replace above declaration with below line.

Map<String,HashMap<String,String>> y = new HashMap<String,HashMap<String,String>>();

If you look at exception you will get an better idea.

Type mismatch: cannot convert from HashMap<String,HashMap<String,String>> to Map<String,Map<String,String>>

It matches exact type. When your given type it might be exact same type. Instead of Map<String,String> you to use HashMap<String,String>

If you want to try another thing please try with below line as well.

Map<String,Map<String,String>> y = new HashMap<String,Map<String,String>>();

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