How to have a key with multiple values in a map?

Question

I have a map like this

Map map=new HashMap();//HashMap key random order.
map.put(\"a\",10);
map.put(\"a\",20);
map.put(\"a\",30);
map.put(\"b\",10);

System.         


        

Answer 1

You shouldn't ignore the generic parameters. What you have is

Map map = new HashMap<>();

if you want to code the solution yourself, you need

Map> map = new HashMap<>();

Anyhow, the preffered way is to use a Guava Multimap